174 STRUCTURAL BOTANY 



between male and female, so generally found in the 

 higher plants, are of only secondary importance, and 

 must be regarded as special adaptations to secure this 

 union with the least expenditure of material and energy. 

 In one word, we may regard conjugation as the primitive 

 form of fertilisation. 



TYPE XII. VAUCHERIA 



We now come to a group of plants, which in their 

 general structure differ more profoundly from all our 

 previous types than any of the latter differ from one 

 another. So far, all the plants we have considered have 

 been cellular : in Vauclieria the protoplasm is not 

 partitioned by cell-walls at all, but is perfectly con- 

 tinuous throughout the whole plant. A large number of 

 green Algae including the extensive family Siphonese 

 are distinguished by this non-cellular structure. Peculiar 

 as these plants are in their internal organisation, they are 

 none the less capable of attaining on their own lines a 

 high development. Many of them are of large size, and 

 some possess organs analogous to the stem, leaf, and root 

 of higher plants. 



Vaucheria is one of the simplest of the non-cellular 

 Algae in its vegetative organs, but as regards its repro- 

 duction is more highly differentiated than any other plant 

 of this type at present known. Some few species of 

 Vaucheria are marine, but most are either fresh-water or 

 terrestrial plants. Some of them are among the very 

 commonest of Algae, occurring everywhere in ponds and 

 ditches, or on damp earth, as, for instance, on the soil of 

 neglected flowerpots, where they form a tangled green 



