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



embryo of Isoetes and that of the typical Monocotyledons; 

 and Kny (1875) has also suggested an independent origin 

 for Monocotyledons from the Filicine£e. The lateral origin 

 of the stem-apex in Isoetes is certainly suggestive of the sim- 

 ilar origin in Naias or AUsma, and Hegelmaier's figures of 

 Pistia are still more suggestive of the embryo of Isoetes, 

 especially in the complete absence of a suspensor. The 

 figures which Solms-Laubach gives of the embryo of 

 Heterachtia, where the suspensor is also absent, are remark- 

 ably like the embryo of a typical Fern. 



The ovules and anthers of Naias probably show the closest 

 approach to the sporangia of the Pteridophytes of any an- 

 giospermous plant. The homologies of the ovules and 

 pollen-sacs of the latter with the sporangia of the former 

 have of course been recognized for a long time. The re- 

 markable similarity to each other of ovule and anther in 

 Naias, even to the investment of the anther with an integu- 

 ment like that of the ovule, is noteworthy as pointing to a 

 very primitive condition in the differentiation of the macro- 

 and microsporangia. It will be borne in mind that in all 

 heterosporous Pteridophytes the two sorts of sporangia are 

 much alike in their earHer stages of development, and it is 

 extremely interesting to find an angiospermous Spermaphyte 

 which so nearly resembles typical Pterido phytes in this re- 

 spect. The writer, in a study of the sporangia in Azolla 

 (Campbell, 1893, p. 162), has called attention to the re- 

 markable resemblance between the macrosporangium there 

 and the ovule of the Angiosperms, a resemblance that did 

 not escape the earHer students of this plant. In this paper 

 I defended the view that the indusium in Azolla is the homo- 

 logue of an ovular integument, a view which I see no reason 

 now to retract. The suggestion has also been made that 

 possibly the velum in Isoetes may be of the same nature. It 

 is true that these may be only analogies, but they are in any 

 case of great importance, as showing how closely related, 

 structurally at least, are the sporangia of the Pteridophytes 

 and Spermaphytes. The different origin of the sporangia 

 in Naias and Isoetes, however, as well as other structural 



