摘要:

Summary.1A detailed investigation of the antheridia in fifteen species of the Florideæ has been undertaken with a view to ascertaining the course of events in the development and liberation of the spermatia. Of the species examined, the antheridial plants were previously entirely unknown in one case (Nitophyllum laceratum); in ten instances (Chondrus crispus, Lomentaria ovalis, Champia parvula, Nitophyllum Hilliæ, Laurencia obtusa, Polysiphonia fastigiata, Halurus equisetifolius, Callithamnion brachiatum, Ceramium rubrum, andFurcellaria fastigiata) little or nothing was known beyond the existence of male plants, and only in four species (Laurencia pinnatifida, Polysiphonia violacea, Griffithsia corallina, andDumontia filiformis) had more or less complete examinations of the structure been made.2It has been shown that in each case a definite number of antheridia are produced sub‐terminally from an antheridial mother‐cell which is specially developed for this function at the apex of a branch or upon the surface of the thallus. The number of primary antheridia from each mother‐cell may be two, and is commonly three, even four or rarely five being found. These antheridia invariably arise as colourless protoplasmic uninucleate outgrowths clothed in the elongated gelatinous wall of the mother‐cell. By the ring‐like ingrowths of this wall at the base, the contents are abstricted and form the single spermatium.3The mature antheridium has been shown to consist of a swollen gelatinous wall surrounding a single apical nucleus, a central vacuole, and a small amount of cytoplasm. The wall is three‐layered; the outermost layer is narrow and deeply staining; within is a gelatinous region which swells greatly at the time of liberation of the spermatium, while around this body is a narrow highly refractive region which may possibly represent the spermatial wall. The spermatium when free measures from 4 to 9 μ in diameter, and in some instances is undoubtedly surrounded by a very delicate wall.4The method of liberation of the spermatium has been studied from unshrunken material, and inLaurenciaandCeramiumhas actually been watched in living material. The exit always takes place by means of a split in the antheridial wall beginning in the swollen apical region and sometimes extending to the base (i. e.Laurencia). Through this narrow aperture the whole contents escape, leaving behind them the empty antheridium as a shrunken gelatinous sheath. In some species, e. g.Rhodymenia palmata, the “cuticle” extending over the thallus is known to peel off in the region of a ripe antheridial sorus, leaving the antheridia freely exposed to the surrounding medium. It has also been demonstrated here, that in other species, e. g.Chondrus, Furcellaria, Ceramium, andPolysiphonia, this does not occur, but the developing antheridia grow upthrough the cuticle until they reachthe surface, where they discharge their spermatia. In no case is the complete antheridium cut off and liberated as described by Yamanouchi forPolysiphonia violaceaor Dunn forDumontia filiformis.5With the exception of the species ofPolysiphonia, observations made on mature plants have shown that secondary antheridia develop within the shrivelled sheath‐like remains of the primary ones, discharging their contents in a similar way. In one species (Callithamnion brachiatum) tertiary antheridia were found.6Cytological investigation shows that the antheridial mother‐cell is always uninucleate. This nucleus divides at the base of each young antheridium, and the daughter nucleus passes into the upgrowing projection. At this stage it is in the resting condition, but as it moves to the apex of the antheridium it passes into early prophase, deeply‐staining granules becoming visible, connected with one another by linin threads. When the spermatium escapes, the nucleus consists of a definite number of chromatin granules or Körnchen united by linin threads. This number never varies within a species, and it is probable that these granules are the true chromosomes.7A classification of the spermatial types among the Florideæ has been drawn up, based on the position of the antheridial mother‐cells and the number of primary antheridia. From this and the preceding investigation it can be seen that while the methods of spermatial production are of little use as a character of systematic importance, yet the fundamental similarity underlying the development in all species points to a

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00509.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1925.tb00510.x

出版商:Blackwell Publishing Ltd    

年代:1925

数据来源: WILEY