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



Startling results have been brought out as yet, nevertheless, 

 a number of interesting and more or less important struc- 

 tural details have been brought to light, which it is hoped 

 will serve for the basis of more extended researches in the 

 future. 



How poorly the affinities of the simpler Monocotyledons 

 are understood is at once evident from the extraordinary 

 divergence of opinion among botanists in their arrangement 

 of genera and families. Thus, Naias is sometimes included 

 with Potaniogeton and Zannichellia in the family of Naia- 

 dacea2(Morong, 1893) ; while on the other hand, most botan- 

 ists at present consider this family to contain only the single 

 genus Naias, while Zannichellia is placed in the Pota- 

 mogetonaceas (Ascherson, 1889) ; and it has been recently 

 suggested that it should stand as a type of a separate family, 

 Zannichelliaceas (Schumann, 1892). These instances will 

 serve to show how urgent is the need of a thorough investi- 

 gation of these doubtful forms, and as the two genera, Naias 

 and Zannichellia, are structurally among the very simplest 

 of the Monocotyledons, they were selected as the first forms 

 for investigation. Both genera, especially Naias, have been 

 examined carefully as to their gross morphology, but the 

 histological details concerning them are very scanty. The 

 most important work done of late years is that of Magnus 

 and Schumann. The former confined his work mainly to 

 Naias, although in his last paper (1894) he also gives some 

 details for Zannichellia; Schumann (1892) has given a 

 fairly full account of the general development of Zanni- 

 chellia; but owing to his depending entirely upon a study of 

 the external structure and not using sections at all, he has 

 made some serious mistakes in his interpretations of the 

 homologies of the floral structures. Most of the work of 

 the earlier botanists was unfortunately inaccessible to the 

 writer, but in Magnus' first paper (1870) there is a very full 

 and clear resume of the results of these observations, to 

 which the reader is referred for further details. 



The writer has confined himself mainly to a study of the 



