174 STRUCTUKAL 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. VAUCHEEIA 



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 Vaucheria the protoplasm is not 

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

 tinuous throughout the whole plant. A large family of 

 green Algse the 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 develop- 

 ment. Many of them are of large size, and some possess 

 organs analogous with the stem, leaf, and root of higher 

 plants. 



Vaucheria is one of the simplest of the Siphoneae in 

 its vegetative organs, but as regards its reproduction is 

 more highly differentiated than any other member of 

 the family as 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 Algse, 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 



