152 THE PHENOMENON OF 



which gave rise to the name of this genus. The branches 

 of the whorls are at the same time the bearers of the 

 fructification, since the spores are formed on particular 

 more vigorously branched and crowded parts of them, 

 through closing off of the terminal cells, while the sterile 

 branchlets, at all events in some species of the genus, run 

 out into capillary points formed of elongated hyaline 

 cells. These branchlets, so strikingly different from the 

 main stem, remind us of the so-called leaves of the 

 Characeae,* and this the more that their lowest cell, as 

 in Chara, gives rise to a peculiar cortical structure ex- 

 tending over the stem, with this distinction, that in 

 Batrachospermum this structure is formed solely of 

 decending rows of cells, while in Chara it is formed of 

 ascending and descending rows, which unite in the middle 

 of the internode. From the rows of cells descending in 

 Batrachospermum from the base of the branchlets of the 

 whorls, and by growing over one another gradually clothing 

 the stem with a many-layered loose rind, which may be 

 compared with the above-mentioned root-like branches of 

 Clicelophora and Coleochtete pulvinata, arise new horizontal 

 branches, by which the spaces between the principal 

 whorls (especially in Batr. vagum and confaswii) become 

 closely filled up with irregular accessory whorls. In 

 addition to the whorl-forming branches, bearing through 

 their limited growth the relation of leaves toward the 

 stem, there occur in Batrachospermum other isolated 

 branches unlimited in their growth, repeating the stem- 



* I have already, in a former passage, in the case otBryopsis (p. 129) and 

 Caulerpa (p. 129), avoided the discussion of the question whether leaves, in 

 the full sense of the term, occur in these lower realms of the vegetable 

 kingdom. It is evident that the organic differences sharply defined in the 

 higher divisions of plants, are only gradually being eliminated in the stage to 

 which the Algae belong, and even in those cases where these differences do 

 present themselves more distinctly, they are connected with the undecided 

 structures by such intermediate stages, that no exact boundary can be 

 drawn. An absolute decision whether or not Algae have leaves, in the full 

 sense of the term, will not be possible until we understand more perfectly 

 the course of development of the leaves of the Phanerogam ia. 



