ALG/E. 211 



long as the term root is arbitrarily applied only to the endogenous leafless shoots ol 

 Vascular plants provided with a root-cap ; but without this arbitrary limitation it woulc 

 be difficult to find a natural boundary-Hne between the root-like outgrowths of manj 

 Algae and the roots of Cormophytes. For the sake of finding an expression for thes( 

 relationships in Algae, and partly also in Characese and Muscinese, the leaf-lib 

 appendages might be termed Phylloids, the root-like appendages Rhizoids. 



The Branching at the growing end of the thallus of Algae may be latera 

 (monopodial) or dichotomous ; very clear examples of both kinds of systems o 

 branching occur among Algae. In both cases the original character may b 

 retained as the growth advances, so that the mature thallome is either monopodia 

 or bifurcate ; or in both cases the further development may be sympodial. Th 

 whole of the ramifications (uniform or not) lie more often in Algae than in othe 

 classes of plants in one plane which bears a definite relation to the horizon, ani 

 is hence probably determined by gravity ; this occurs, apparently, especially i: 

 dichotomies. Those cases are of special morphological interest where the branche 

 of a true or spurious dichotomy are closely packed laterally, so that they forr 

 roundish discs lying upon the substratum, which continue to grow centrifugally a 

 the margin (as in Coleochaete and jNIelobesiaceae). 



The Mode of Reproduction is not yet accurately understood in all families c 

 Algae, but in many it has been carefully investigated by distinguished observers an 

 is even better known than anywhere else in the vegetable kingdom. As in th 

 vegetative organs of the plant, so also in the reproductive, an enormous diversit 

 is exhibited. Asexual reproduction is known in all the sections of Algae, sexuj 

 reproduction in many, some of which belong to the simplest but most to the mor 

 highly- developed groups ; in numerous cases we find an alternation between asexuj 

 and sexual generations. 



Asexual Reproduction is brought about either by motionless or motile sporei 

 Motionless asexual reproductive cells are found not only in the very simply cor 

 structed Rivularieae, but also in the most highly developed Florideae (in this cas 

 generally as so-called Tetraspores). Motile reproductive cells (Swarm-spores c 

 Zoospores), are especially common in those sections where the chlorophyll i 

 not concealed by other colouring materials (Chlorosporeae, Confervae). The 

 result from the contraction of the protoplasmic substance of certain cells (nc 

 unfrequently accompanied by division), which is then reconstructed as a primordii 

 cell, and escapes through an opening in the wall of the mother-cell or, after il 

 dissolution, into the surrounding water, where the naked swarm-spore now move 

 with a rotatory and at the same time progressive motion for some minutes, hours 

 or even days, until it finally comes to rest, becomes fixed to one spot, and germmates 

 In every swarm-spore there may be distinguished an anterior hyaline end, usuall 

 pointed, which is turned foremost during movement, and a posterior thicker roundei 

 end provided with chlorophyll. The line which unites the two ends is the axis o 

 growth of the swarm-spore, and of the embryo-plant which grows from it. Whei 

 the swarm-spore comes to rest, it fixes itself by its anterior hyaline end, and form 

 there a hyaline organ of attachment (rhizoid), which is often branched, while tb 

 coloured posterior end becomes the free apex of the young plant. The rotating 

 advancing movement is occasioned by Cilia, fine vibratile threads which are sometime 



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