963 resultados para vegetative buds
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The toxicity of the herbicide glyphosate was tested on water hyacinth (Eichhornia crassipes) samples cultivated in glass aquariums. The lowest dose (0.09 g.m-2) leads to an increasing plant growth rate. This growth rate decreases with intermediate doses (0.18 and 0.36 g.m-2), the consequence of which is to increase stolons (vegetative reproduction). On the other hand, the dose of 0.72 g.m-2 leads to a total and irreversible destruction of plants.
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103 p.; 102 p.
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Mats (biomasses) of macroalgae, i.e. Ulva spp., Enteromorpha spp., Graciolaria spp., and Cladophora spp., have increased markedly over the past 50 years, and they cover much larger areas than they once did in many estuaries of the world. The increases are due to large inputs of pollutants, mainly nitrates. During the warm months, the mats lie loosely on shallow sand and mud flats mostly along shorelines. Ulva lactuca overwinters as buds attached to shells and stones, and in the spring it grows as thalli (leaf fronds). Mats eventually form that are several thalli thick. Few macroinvertebrates grow on the upper surfaces of their thalli due to toxins they produce, and few can survive beneath them. The fish, crabs, and wading birds that once used the flats to feed on the macroinvertebrates are denied these feeding grounds. The mats also grow over and kill mollusks and eelgrass, Zostera marina. An experiment was undertaken which showed that two removals of U. lactuca in a summer from a shallow flat in an estuarine cove maintained the bottom almost free of it.
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本实验用喷施6-BA和茎切生根的方法建立了一套德国鸢尾快速分株繁殖的体系。用3 000 mg/L 或5 000 mg/L 的6-BA 对德国鸢尾(Iris germanica)‘lovely again’进行单次喷施可以促进根茎芽的萌发和根状茎的形成。在喷施后的30 天到90 天内,BA的促进作用在具有2个或4个起始根状茎的植株上表现得很显著,但对于只有一个起始根状茎的植株不显著。在喷施后的150 天以及第二年,具有2个或4个起始根状茎的母株总体上比只具有1个起始根状茎的母株产生了更多的根状茎。而6-BA的喷施对母株的叶面积和叶片数变化没有显著影响。在早春时,把处于不同发育阶段的侧芽或小根茎从母株上取下,并且用不同浓度的IBA处理。总体上,处于较高发育阶段的茎切(芽切)在生根率、初级根和次级根的数目,总根长、根干重以及植株高度等测量指标方面的表现较好。IBA对德国鸢尾的茎切(芽切)的生根作用不显著。多次喷施6-BA 对德国鸢尾根茎芽的生出的促进作用显著,并且使生物量重新分配。连续喷施6-BA后,对内源生长素和细胞分裂素的连续测定结果表明,6-BA的作用主要是解除了顶端优势对侧芽的萌发和生长的抑制,从而形成新的根茎。
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Estuaries provide critical nursery habitat for many commercially and recreationally important fish and shellfish species. These productive, diverse ecosystems are particularly vulnerable to pollution because they serve as repositories for non–point-source contaminants from upland sources, such as pesticide runoff. Atrazine, among the most widely used pesticides in the United States, has also been one of the most extensively studied. There has not, however, been a specific assessment of atrazine in marine and estuarine ecosystems. This document characterizes the presence and transformation of atrazine in coastal waters, and the effects of atrazine on marine organisms. Review of marine and estuarine monitoring data indicate that atrazine is chronically present in U.S. coastal waters at relatively low concentrations. The concentrations detected have typically been below acute biological effects levels, and below the U.S. EPA proposed water quality criteria for atrazine. While direct risk of atrazine impacts are low, uncertainty remains regarding the effects of long-term low levels of atrazine in mixture with other contaminants. It is recommended that best management practices, such as the use of vegetative buffers and public education about pesticide use, be encouraged in the coastal zone to minimize runoff of atrazine into marine and estuarine waters.
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本实验通过对菘蓝(Tsatis Japanica)的六种外植体进行培养并诱导分化,研究了不同的外植体在相同培养条件下器官分化的不同状况并以分化周期最短、分化频率最高的根外植物为实验材料,通过改变外源激素的配比和浓度,以及其池培养条件的变化来控制外植体定向分化.对培养根段中不定芽的发生途径,做了完整的组织学和扫描电镜观察,并用不定芽做了人工种子的包埋,初步进行j,菘蓝人工种子的研究。
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诱导风信子(Hyacnthus orientalis L.)同一花被外植体上不同部位细胞分化花芽,从外源激素的作用和内探激素的变化探讨细胞脱分化启动的原因,研究了不同外源激素的组合下同一花被不同部位花芽分化的诱导频率:测定了花被上、中,下三部位切块离体培养前后的内源IAA和Z+ZR的含量;在此之前研究了GC-MS.MIM内标法测定微量植物材料内源IAA含量的可行性. GC-MS.MIM内标法是测定微量(0.5-1g)植物材料内源IAA含量的一种比较理想的方法,所需材料量一般为0.58.这一方法的材料前处理采用粗提液用C18Sep-pak柱初步分离纯化.HPLC进一步纯化,能获得纯度高的样品,且操作简便,省时省力. 风信子同一花被不同部位细胞均能分化花芽.当培养基中附加2.0mg/l Zeatin或2.0mg/16-BAP时,随着外探IAA浓度从0升高到10.0mg/l.捆胞分化花芽的部位从花被下部向上部移动。 离体培养前后同一花被上、中、下三部位内源IAA和Z+ZR含量测定结果表明.风信子同一花被内源IAA含量是上部最高,下部次之,中部最低,而内源Z+ZR含量从上向下依次增加;在附加不同外源激素的MS培养基上培养3天后,同一花被上,中、下三部位内源IAA和Z+ZR含量部有一定的变化。
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辽东栎是我国暖温带落叶阔叶林主要优势种之一。它具有很强的萌蘖能力,在东灵山地区存在于多种林分中,并成为辽东栎林和落叶阔叶混交林的优势种。本文以植物种群构件理论为基础,对辽东栎的种子、幼苗、幼树和成体四个阶段不同侧面进行了调查统计和试验分析。初步得出如下结果: 1. 种子库统计表明:(1)种子雨持续时间短、强度大,种子散落总密度为123个m~2。(2)土壤种子库存在时间约100天左右,种子密度最高时为42.7个/m~2。(3)土壤种子库输出途径主要有死亡后腐烂、发芽、动物当场取食和搬运,其中动物搬运是影响种子库动态的最重要因子。(4)动物搬运和取食是影响种子命运的主要因素,如果没有该因素的影响,辽东栎能够完成从种子到幼苗的过程;(5)被啮齿动物贮藏的种子大多被取食,极少存活;(6)地表覆盖物能减少动物搬运、取食的影响,但对成苗效果不明显。 2. 干旱处理和模拟去叶试验的结果表明:(1)干旱将显著降低单叶面积、叶面积比和叶比重,从而也显著降低了单株生物量,但根比重却较对照组有显著上升;(2)去叶显著提高了单株叶数、叶面积比和叶比重,尽管单株生物量只稍高于对照组。这说明了辽东栎幼苗在去叶后具有一定的补偿能力。 3. 芽的命运调查发现:(1)辽东栎的芽或保持休眠状态,或死亡后脱落,或分化为营养枝、雄花枝、雄花序、雌花枝和两花枝等;(2)不同生境中芽的命运不同,生活在林窗中的幼树上的芽分化为具有生殖功能的枝条的比例高于郁闭林中的幼树,而与成熟个体接近;(3)同一个体内部,上层芽分化为生殖枝的比例明显大于中、下层;(4)芽的命运与枝长关系密切,长枝上的芽分化为生殖枝的可能性较大;(5)结实枝的平均枝长、枝上平均叶数都明显高于非结实枝。 4. 构型分析表明:(1)不同发育阶段的辽东栎个体的分枝格局不同:幼苗阶段,高生长显著,枝条伸长较快,但分枝率低;幼树阶段,分枝率显著小于成株阶段;但上层枝条的平均枝节倾角大于其它两阶段,上层枝条的长度也大于成株阶段;成株阶段,冠幅迅速扩展,分枝率较前两时期显著增加,同时顶端优势减弱,引起休眠芽萌生苗的发生。(2)不同生境的辽东栎个体分枝格局也有较大差异:混交林中的辽栎个体多生活在林隙中,同灌丛中的个体相比,枝冠窄小,枝倾角较大,第一枝级枝条(上层)较长,但分枝率较小叶面积指数较低;枝、叶的方位角,叶倾角(上层)在不同生境中未发生显著变化。 5. 叶群体统计表明:(1)不同个体,同一个体内部不同层次,叶数量动态趋势都基本一致。现叶期和叶落半衰期很短,现叶方式为爆发型;(2)不同个体间叶期差异很大,暗示在辽东栎种群内部或许存在有强烈的遗传分化。 6. 对叶的生长和光合作用测定发现:(1)辽东栎叶的长度、面积和干重的增加有共同趋势:即在叶生长早期增加很快,其后渐渐降低,叶长度、面积约在六月初达极大值,叶干重稍后达极大值;(2)净光合速率在整个生生季里随叶的生长发育是先上升,至七月中旬达极大值,然后逐渐下降;而暗呼吸速率除在落叶前有微弱上升外,一直都处在下降状态;(3)叶的净光合速率日进程具“午休”现象,可能由高温和强光照引起;(4)叶的形成初期,碳的输入较高,展叶后约十天左右,输入输出达到平衡;碳输出在七月中旬达极大值,随后下降。可见:(5)叶的光合能力与叶的生长发育状况有密切关系。 7. 对叶养分季节动态的测定表明:(1)N、P、K、Ca、Mg、Fe等6种元素的浓度和贮量在叶的生活史中都发生了明显的季节变化,其中N、P、K等3种元素的浓度在展叶初期下降很快,随后逐渐下降的,但贮量是在7月下旬达到最大值;(2)Ca浓度和贮量整个生长季中一直保持上升趋势,Mg的季节变化无一定规律;(3)N、P、K、Mg都有一定程度的回收,其中N、P的回收率分别为67%和,Ca、Fe在叶中有所积累。 对栎属植物养分动态的比较分析表明:(1)落叶植物成熟叶中的N浓度显著高于常绿植物,但N、P的回收率与成熟叶中的浓度无明显相关性;(2)栎属植物的成熟叶和落叶中的N、P浓度间呈显著相关。
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1.对四川省岷江上游地区(茂县)的锐齿槲栎(Quercus aliena var. acuteserrata)天然次生林进行研究,发现:(1) 坚果完好比例约在14% ~26%之间,完好坚果的发芽率和发芽势都比较高,但在天然状况下能够留存到翌年5月的坚果几乎没有。因此,实生幼苗的天然补充就受到了严重的限制。(2) 林缘的幼苗密度低于所有其它生境的 (P<0.05),林中的幼苗密度最高,和林窗的比较有显著差异(P<0.05), 而和灌丛的比较则差异不显著(P>0.05)。在灌丛幼苗密度和林中以及林窗的比较都没有差异。动物对坚果的取食速度则是林中的最慢 (10.0%),林窗和林缘的基本相同(分别为61.1%和66.5%),取食速度都明显快于林中(P<0.01)。(3) 林中的幼苗在小于100 cm的各高度内都有大量分布,说明在林中树冠下幼苗是可以长期存在的,暗示在幼苗阶段的锐齿槲栎可能是耐荫的。(4) 在林中缺失幼树,在林缘则有包括幼树在内的完整的更新大小系列,表明林缘是更新的关键地点。(5) 在栎林的每一个大小级别上,萌生个体和实生个体都按各种比例伴生,说明导致萌生的干扰一直在发生,并可能在森林的更新中扮演重要角色;也说明该地区的锐齿槲栎林由萌生和实生起源的个体混合组成。 2.栎林是北半球温带森林的重要组成部分,因此栎林更新是全球森林更新研究的热点之一,而啮齿动物对栎林更新的影响则是关注的焦点。在2002~2003年,通过坚果标记研究了未被取食和遗弃坚果(即咬开后只有少部分被捕食后丢弃在林中的坚果)的健康比例,并定量测定了坚果的捕食、搬运、遗弃、丢弃、贮藏和留存等各种命运的比例和特点;对坚果也进行了各种人为的处理,以观测其命运和动物取食速度,发现:(1) 遗弃坚果中不健康坚果的比例比动物未取食的天然坚果中的比例有极显著的增加 (P>0.05),暗示啮齿动物一般是通过咬开坚果来识别坚果健康与否并决定是否捕食。(2) 根据坚果命运和对照相比改变与否以及如何改变,各种人工处理坚果的命运可以分为 4 类:① 坚果命运没有任何显著改变;② 坚果被就地捕食的速度降低,搬运的速度不变,最终搬运坚果的比例增加而就地捕食坚果的比例降低,留存坚果的比例偶尔能增加至0.2%;③ 坚果就地捕食的速度几乎降至0,搬运的速度则在下降一段时间后又上升,并且搬运作用持续了相对长的时间,最终搬运坚果的比例大大增加,就地捕食坚果的比例很低,留存率为0;④ 坚果被搬运和就地捕食的速度和比例都降低,留存坚果的比例相应的大大增加,甚至可以达到50%。(3) 命运得到显著改变的②、③、④类坚果所承受的人工处理按照作用方式又可以分为主要作用于坚果化学状态(即气味浓度)的处理、主要作用于坚果物理状态(颜色、形态、有无附属物等)的处理以及使坚果处于不同颜色背景的处理;其中主要作用于坚果化学状态的处理对坚果命运具有最重大的改变,如胶带包裹处理和烧焦处理;其它各种主要作用于坚果的物理状态和所处背景的处理对其命运则也具有相对轻微的改变。这一试验结果可能证明:啮齿动物在对坚果进行识别和取食选择等活动时主要依赖于嗅觉来感知坚果的可食性,但是能感觉物理状态和所处背景的视觉也起一定程度的作用。(4) 啮齿动物对栎树坚果进行就地捕食、遗弃、搬运、异地捕食、丢弃、贮藏等作用,使各种命运的坚果都具有一定的数量比例和特点,也提供了动物影响栎林更新的多种可能途径。 3.人工干扰是任何退化生态系统中都始终存在的重大问题。除了明显的砍伐或者采摘外,人工践踏也是一种重要的干扰,特别是在茂县的山林普遍被牛马不断的放牧的情况下,这个干扰的后果就更加显著。为此研究了人脚踩踏的路上的白车轴草和未踩踏草坪上白车轴草在最大叶长、株高、芽高、构件数量、构件平均鲜重、死叶数量、根长等构型指标,根、茎、叶三者的生物量(干重)及比例等生物量指标,平均花序数量、花平均数量等繁殖指标方面的不同,发现踩踏使白车轴草植株:(1) 株高降低,芽高降低,最大叶长变小,平均每厘米的构件数量增加,构件平均鲜重降低,根长度减小,死叶数量增加。(2) 平均花序数量下降,每花序的花平均数量下降。(3) 但是在生物量的分配上,根和茎的生物量没有显著的下降,但是叶的生物量显著减低。因为白车轴草的茎可以不断克隆繁殖,所以踩踏对其存活可能没有太大的影响,只是造成了植株的矮化和密集化,根也变短;但是对种子繁殖有重大影响,反映在平均花序数量和每花序平均花数的显著下降上。在生物量的分配中,作为主要的同化器官,叶的生物量显著下降,而根茎比没有变化。这可能说明这样的克隆植物其物质流动是呈现网络化的特征,具有比较强的抗干扰能力。 4.连香树、油松、日本落叶松、华山松油松混合林是茂县地区的几种主要的已经营造的林型或者树种。为了了解其20年来的营林效果,运用样方调查的方法测量了这几种树种或者林型的胸径、持水量、凋落物现存量、密度等,评价了它们在生长、营业循环和水土保持等方面的差异。结果表明:日本落叶松具有生长缓慢,凋落物现存量大,涵养水分能力良好的树种,值得推广;油松生长迅速,凋落物现存量巨大,涵养水分能力一般的树种,也可以大力栽植;油松和华山松的混交林具有比较大的蓄积量和较好的涵养水分的能力,可以推广;而连香树则做为生长速度中等,成材率低,凋落物现存量小,涵养水分能力差的树种,不应该进一步推广。
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In order to study the early developmental stages of Nandus nandus an experiment was conducted, where eggs and milt were obtained from the laboratory reared N nandus by stripping after 15 hours of 150 mg/kg body weight of carp PG extract injection. Then the eggs were fertilized in the laboratory and subsequent developmental stages were studied. First cleavage (two cell), four cell, eight cell, sixteen cell and multi cell stages were found 30, 50, 70, 105 and 160 minutes after fertilization respectively. Morula, early gastrula, middle gastrula, late gastrula and yolk plug stages were found 5, 8, 9, 11 and 13 hours after fertilization respectively. Hatching occurred within 20±2 hours after fertilization, and larvae were measured 1.60 mm in diameter. After one hour of hatching two melanophore bands were found at the caudal region of the body of the larvae. Eyes were first observed in l 0 hours, pectoral and pelvic fin buds appeared in 22 hours and well developed in 38 hours old larvae. Mouth cleft and brain lobes were visible when the larvae were 34 and 38 hours old respectively. Myomeres partially appeared in 16 hours, which were clearly visible in 74 hours old larvae. Larvae started wandering and searching for food after 56 hours of hatching. The yolk sac was completely absorbed when larvae became 62 hours old.
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The origin of eukaryotic flagella has long been a mystery. Here we review the possibility that flagella sprouted evolutionarily from the eukaryotic cell proper seems very unlikely because it is hard to imagine what function and benefit in natural selection the flagella would have provided to the cells when they first emerged as simple buds. Lynn Margulis' 1970 spirochete hypothesis, though popular still, has never been confirmed. Moreover, the absence of tubulin and axonemal dynein in the spirochetes and the incapability of the bacterial and eukaryotic membranes' making a continuum now suggest that the hypothesis is outdated. Tubulin genes were recently identified in a new bacteria division, verrucomicrobia, and microtubules have also been found in one of these species, epixenosomes, the defensive ectosymbionts. On the basis of these data, we propose a new symbiotic hypothesis: that the mid-ancestor of eukaryotic cells obtained epixenosomelike verrucomicrobia as defensive ectosymbionts and the ectosymbionts later became endosymbiotic. They still, however, protruded from the surface of their host to play their role. Later, many genes were lost or incorporated into the host genome. Finally, the genome, the bacterial membrane, and the endosymbiotic vesicle membrane were totally lost, and fingerlike protrusions with microtubules formed. As the cells grew larger, the defensive function of the protrusions eventually weakened and then vanished. Some of the protrusions took on a new role in cell movement, which led them to evolve into flagella. The key step in this process was that the dynein obtained from the host evolved into axonemal dyneins, attaching onto the microtubules and forming motile axonemes. Our hypothesis is unproven, but it offers a possible explanation that is consistent with current scientific thought. We hope that our ideas will stimulate additional studies on the origin of eukaryotic flagella and on investigations of verrucomicrobia. Whether such studies confirm, refine, or replace our hypothesis, they should nevertheless further our understanding of the origin of eukaryotic cells.
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The timing of the floral transition has significant consequences for reproductive success in plants. Plants gauge both environmental and endogenous signals before switching to reproductive development. Many temperate species only flower after they have experienced a prolonged period of cold, a process known as vernalization, which aligns flowering with the favourable conditions of spring. Considerable progress has been made in understanding the molecular basis of vernalization in Arabidopsis. A central player in this process is FLC, which blocks flowering by inhibiting genes required to switch the meristem from vegetative to floral development. Recent data shows that many regulators of FLC alter chromatin structure or are involved in RNA processing.
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Recent transcription profiling studies have revealed an unexpectedly large proportion of antisense transcripts in eukaryotic genomes. These antisense genes seem to regulate gene expression by interacting with sense genes. Previous studies have focused on the non-coding antisense genes, but the possible regulatory role of the antisense protein is poorly understood. In this study, we found that a protein encoded by the antisense gene ADF1 acts as a transcription suppressor, regulating the expression of sense gene MDF1 in Saccharomyces cerevisiae. Based on the evolutionary, genetic, cytological and biochemical evidence, we show that the protein-coding sense gene MDF1 most likely originated de novo from a previously non-coding sequence and can significantly suppress the mating efficiency of baker's yeast in rich medium by binding MAT alpha 2 and thus promote vegetative growth. These results shed new light on several important issues, including a new sense-antisense interaction mechanism, the de novo origination of a functional gene, and the regulation of yeast mating pathway.
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Water hyacinth is a free-floating waterweed native to the Amazon River Basin in South America. In its native range, water hyacinth is not an environmental problem, although the weed is one of the most invasive alien plants in freshwater environments. Water hyacinth has the potential to become invasive through fast vegetative reproduction and rapid growth to accumulate huge biomass and extensive cover in freshwater environments. Over the last 150 years water hyacinth has invaded most countries in the tropics and sub-tropics, introduced by man, mainly for ornamental purposes. Such introductions led to the infestation of most freshwater-ways in the southern United States of America, parts of Australia, the pacific islands, and most countries in Asia and Africa. The extensive tightly packed mats of water hyacinth are often associated with devastating socio-economic and environmental impacts. Invasion by the weed has, therefore, often generated urgent costly problems associated with the weed biomass and its management. A classic example of such problems was triggered by the invasion and proliferation of water hyacinth in the Lake Victoria Basin during the 1980s (Freilink 1989, Taylor 1993, Twongo et al., 1995). The weed infestation marked the beginning of a decade of intensive and systematic campaign by the three riparian states (Kenya, Tanzania and Uganda) to bring weed proliferation under control. The discussions in this Chapter span over ten years of dealing with the challenges paused by the imperative to manage infestations of water hyacinth in the Lake Victoria Basin. The challenges included the need to understand the dynamics of water hyacinth infestation; its distribution, proliferation and impact modalities; and the development and implementation of appropriate weed control strategies and options. Most specific examples were taken from the Ugandan experience (NARO, 2002).
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The present paper gives a full description of the organization of Acanthococcus antarcticus Hooker et Harvey, a not well known member of the Rhodophyllidaceae as well as gives for the first time description of the male and tetrasporic plants. Detailed organization of the carpogonial branches, spermatia and tetraspores is also presented. Nineteen figures illustrate the text (material collected at Deseado port, Santa Cruz prov., Argentina). The following text is the content of the discussion. From the description it is possible to confirm the position of Acanthococcus in the Rhodophyllidaceac as was done by Kylin (Kylin 1960, p. 290 et seg.). It has many similarities in the development of the carpogenic branches and in the formation of spermatia as well in the production of the zonately divided tetrasporangia with the genera of the family whose reproduction is known; Cystoclonium purpureum (Hudson) Batters and Rhodopyllis bifada (Good. et Woodw.) Kützing (Kylin 1923); Calliblepharis jubata (Good. et Woodw.) Kützing (Kylín 1928) and Craspedocarpus erosus (Hook. et Harvey) Sehmitz (Kylin 1932). Apparently the distinguishing feature of Acanthococcus is the structure of the vegetative frond, with the abundant development of rhizoidal filaments in the medula, besides the characteristic appendages of the cystocarps. Harvey's figure (Harvey 1847, P. 181, Fig. 3) of the tranverse section of the plant shows the central portion composed of a dense small-celled medula limited by a region of large cells which is externally covered by a small-celled cortex. As we have seen the small-celled filaments are not restricted to the central portion, but extend into the large-celled portion and can reach the cortex. On the other hand, the eros section of Acanthococcus depicted by Kützing (Kützing 1867, T. 93, Fig. h, under Callophyllis antartica), apparently belongs to another plant, so different in the structure when one compares his figure with Harvey's and the ones in this paper. RESUMEN EN ESPAÑOL Este trabajo presenta una completa descripción de la organización de Acanthococcus antarcticus Hooker et Harvey, un miembro poco conocido de las Rodofilidáceas, así como presenta por primera vez descripciones de las plantas masculinas y de las tetraspóricas. También por primera vez es presentada la organización detallada de las ramas carpogoniales, de los espermecios y de las trásporas. Diecinueve figuras completan el texto (material coleccionado en Puerto Deseado, Prov. Santa Cruz, Argentina).