﻿66 DEBY'S RESEARCHES ON THE CRYPTOGAMIC FLORA. 



its own brood, but in its descendants of the \i.th or 15th compound generation. We 

 might carry on this comparison much further, but as we believe it to be a simple 

 analogy with the facts stated by Steenstrup as existing in the Medusas, Polypes, 

 Corallines, &c, and no identity, we prefer not prolonging here what we consider to be 

 useless and sterile discussion, and Ave shall at once pass to the second manner of in- 

 vestigating the matter, which seems more consistent with philosophical induction as 

 applied to Algology. 



2. All plants are produced by the multiplication of a simple cell, which in the 

 cryptogamia is called a spore. If Ave folloAV out the subsequent development of such a 

 spore, Ave observe it generally to j)roduce a succession of vegetative cells (not spores), 

 until haA T ing at last attained maturity, (having produced a determined number of 

 such cells) it forms one or seA^eral peculiar cells of a different nature from the antece- 

 dent one. These last are the real spores destined to produce a new succession of 

 vegetative cells, and after these a second generation of spores. The cells formed ante- 

 riorly to the spores are generally connected together by cohesive or intercellular sub- 

 stance, so as to form a parenchymatous mass, or thallus. The formation and deposi- 

 tion of cells may take place according to three dimensions of space. It may take 

 place in length (in a linear direction), and we have a filamentous (articulated) thallus, 

 as in Conferva, Zygnema, &c. It may take place in length and in breadth simulta- 

 neously, and we haA r e a foliaceous thallus, as in the Ulvacae, &c. ; or, lastly, it may 

 take place in length, breadth, and height (thickness) at the same time, and we obtain 

 a massive parenchymatous thallus, Avhich may be regular or irregular. 



In the deA^elopment of Chlamidococcus in a damp place, or when kept humid, as 

 above described, Ave have an exemplification of an alga produced by an ordinary 

 spore, and consisting in an irregular foliaceous thallus, which, after growing for a 

 determined time (by production of new vegetative cells) dies away, all but the last 

 formed spores, Avhich remain dormant until called into life by external circumstances. 

 May we not consider also the development of the Chlamidococcus, immersed in 

 water, as a growing plant, in which the ordinary vegetative cells are free (instead of 

 being united into a so-called compact thallus) and in which the terminal or last formed 

 cells, just as in other alga?, end by giving birth to spores ? I think analogy and mor- 

 phological considerations lead to the adoption of this manner of vieAving the subject. 

 In fixed alga? the cells are immovable, and united to one another in the thallus ; in 

 the form under consideration they differ only in being free and being furnished with 

 prolongations of the inner cell membrane, which give them for a short period limited 

 locomotive powers. In the crustaceous form of Chlamidococcus, Avhere these flagel- 

 liform organs would be useless, we find them to be Avanting, and yet the plant is 

 fertile that is, bears at last well-formed spores at the surface of its thallus, so that we 

 may consider these curious appendages of very secondary importance in the organic 



