38 SURVEY OF THE REPRODUCTIVE PROCESS 



continued growth and occasional branching out of the frond 

 by the addition of new component cells, but independent 

 fronds are also sometimes produced by detachment of 

 bulbils or other portions of the substance of a pre-existing 

 one ; and, besides this, almost all the species bear more 

 than one kind of sporoid bodies. We are not, however, in 

 a position to say whether, or in what way, spore-gemmation 

 alternates with sexual generation generally throughout the 

 group. We only know that in a few species a gamomorphic 

 porthallium is budded off from the spore for the develop- 

 ment of the reproductive organs of one of the sexes, and 

 that some of the same species (CEdogonium and its allies) 

 are also the subjects of a sort of gemmation in the proto- 

 morphic stage, as well as certain fucoids the spores which 

 actually germinate into new fronds being only a secondary 

 product of impregnation ; while in other cases (some Floridese 

 as Ceramiurn) there are certain theoretical grounds for sup- 

 posing that the sexual fronds may originate from the tetras- 

 pores of the gemmiparous fronds. 



A few words may be added in reference to the order 

 Characea3, on the systematic position of which botanists are 

 not quite agreed. These plants are described by Berkeley 

 as consisting " of confervoid articulated threads, simple as 

 in Cladophora, or compound as in Potysiphoma"* In their 

 vegetative axis, therefore, they have quite the organization 

 of the true Algse, and though their reproductive organs are 

 certainly very peculiar, they are perhaps reducible to a mo- 

 dified form of the same general type. Two kinds of fructi- 

 fication are met with in Ckara, the nucule and the globule, 

 which are supposed to contain respectively the germinal and 

 spermatic elements. This opinion rests mainly on the de- 

 velopment in the latter of articulated filaments, containing 

 motile ciliated bodies, having a great general resemblance 



* Cryptogamic Botany, 425. 



