6 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



A. — Naias. 



The most important contribution to our knowledge of the 

 genus Naias we owe to the admirable monograph of the 

 genus by Magnus (1870). In the introduction he has given 

 a very clear and satisfactory resume of the work done by 

 earlier observers, from Vaillant's account in 1719, up to the 

 time of the publication of his own memoir. He has also 

 written the account of the Naiadaceae in Engler and Prantl's 

 " Die natiirlichen Pflanzenfamilien " (1889), and still more 

 recently a paper in the ' ' Berichte der deutschen botanischen 

 Gesellschaft " (1894). He clearly made out the relation of 

 the floral parts and the anatomy and histology of the mature 

 plant and fruit, as well as the general facts of germination ; 

 but he gives no account of the histology of the growing 

 parts of the flowers. He also gives no account of the em- 

 br3^o, beyond a reference to the gross anatomy of the embryo 

 in the ripe seed. 



Schumann (1892) has also investigated the structure of 

 Naias, but, like his predecessors, pays no attention to the 

 minute structure of the floral parts. His results agree in 

 the main with those of Magnus, but he does not agree with 

 the latter in considering the envelope surrounding the ovule 

 as a peculiar structure, but, in common with other botanists, 

 regards it as a carpel, a view which Magnus vigorously 

 opposes. 



My own observations were based entirely upon Naias jlex- 

 ilis Willd., the only available species, and it will be neces- 

 sary to examine critically other species before we can 

 generalize as to results. It is true that all those so far 

 examined agree closely in most of their details; but as in 

 N. jlexilis there is a considerable degree of variation in cer- 

 tain structures, especially in the embryo-sac, it is highly 

 important that these should be compared with the correspond- 

 ing ones in the other species. 



The material used was collected in the Detroit river, but 

 the species is of wide distribution in the United States and 

 occurs in certain parts of California. 



