296 STRUCTURAL BOTANY 



The sexual process in Florideae is quite peculiar 

 among Algse, for no definite oospore is ever formed as 

 the result of fertilisation. The whole carpogonium 

 when fertilised remains in complete continuity with the 

 tissues of the thallus, and sends out branches, which 

 ultimately produce numerous spores, usually after various 

 subsidiary cell-fusions have taken place. This continuity 

 of the spore-fruit with the thallus completely severs the 

 Florideae from the Bryophyta, with which there is other- 

 wise a certain analogy, in so far as in both groups the 

 result of fertilisation is a fruit. The Florideae are also 

 remarkable for the entire absence of motile ciliated cells, 

 a point in which they differ from the great majority of the 

 Algse, though certain isolated groups, such as the Conjugatae 

 (which certainly have nothing to do with them), have the 

 same peculiarity. We must await the results of further 

 investigation before anything definite can be said as to 

 the affinities of the Eed Seaweeds. 



The Phaeophyceae are also much isolated from other 

 Algae, but they have more in common with Chlorophyceae 

 than is the case with the Eed Seaweeds. Ciliated cells 

 are almost universal throughout the group, though in 

 the highest Brown Algae the Fucaceae they only 

 appear as spermatozoids. Fertilisation, so far as known, 

 always takes place outside the oogonium, a point in which 

 these plants differ from the Green Algae. The Fucaceae 

 are on a much higher level than the rest of the order, 

 but transitional forms are not altogether absent. On the 

 whole, we may say that the Brown Algae are a natural 

 group, attaining very great complexity on their own 

 lines, and not clearly related, either to the lower or higher 

 families, though an affinity to some of the Green Algae 

 is not altogether out of the question. 



