Evolution of Plants 315 



ochcete — or non-ciliate and fixed egg cells mth small biciliate 

 sperm cells as in Coleochcete, the transition stages are graded 

 and suggestive. 



Along this advancing chain of types the plants show green 

 branching cellular threads that at times tend to form flattened 

 cell plates as in Ctenocladus, Endoclonium, and some species 

 of Coleochcete. They all possess one chromatophore of con- 

 siderable to large size, or which may divide into 5-8 separate 

 masses. All moreover are fresh- water genera fundamentally, 

 for the few species that are now brackish or salt-water are 

 evidently derivatives from fresh- water ancestry. 



From the above cited evidence we would suggest that two 

 main lines of evolutionary advance started which may be 

 termed (a) the biciliate and (b) the polyciliate spermatial 

 lines. As will be discussed later, both persisted during their 

 earlier advance as fresh-water organisms, but gradually a 

 palustral and then a land stage was established, that started 

 the biciliate spermatial branches of the Bryophyta and prob- 

 ably the Lycopodinese; and the polyciliate spermatial branches 

 of the Filicinese, Pteridospermese, and Metaspermese. Con- 

 sideration of this will be taken up in later pages. Meanwhile 

 we will continue the probable history of the algoid derivatives. 



The Cladophoracese, Vaucheriacese, and Characese are either 

 wholly or largely fresh- water groups. As stated by Wille 

 {100: 117) the first suggests decided affinity through Urospora 

 and Rhizoclonium mth Hormidium and other representatives 

 of the Ulothricacese, while all are allied to the Chsetophoracese. 

 But, like the Ulvacese of very different structure and affinity, 

 a decided tendency to migration into brackish and then into 

 salt water is showTi. So there seems early to have originated, 

 probably from the Tetrasporacese and more advanced types, 

 an abundant and common ancestral assemblage such as is 

 feebly represented now by Gomontia, Botrydiuniy and Phyl- 

 losiphon, and from these on the one hand started the unicellular 

 fresh-water Vaucheria and the marine series of the Cauler- 

 pacese and Codiacese, while on the other started the multi- 

 cellular fresh-water Cladophora, Cylindrocapsa, Pithophora, 

 Sphceroplea, and the Characese, as well as the salt-water Valon- 

 iacese and the Dasycladiacese. 



During this process of evolution the single chromatophore 

 of tetrasporaceous and ulothricaceous character became ex- 

 tended over the protoplasm as a uniform or banded or reticu- 

 late expanse that developed one or more pyrenoids; or, as 

 in some species of Cladophora, sent reticulate extensions inward 

 toward the center; or, as in other species and in the Characese, 



