( 830 ) 



voiing seed. Wlien a row of four cells has thus arisen, the three 

 which are turned towards the micropyle become a snspensor, while 

 the fourth divides b}' a wall at right angles to the previous ones 

 and becomes the embryo proper. 



I have not traced the further development of the embryo, partly 

 for want of suflicient material, but especially because Warming 

 has already fui-nished an excellent treatise dealing with this 

 subject, and illustrated with figures. Considering the many new 

 facts, which Willis has discovered about the germination of the 

 Podostemaceae of Ceylon, an investigation of the American forms in 

 this direction would certainly repa3% since through Goebel we have 

 only learned in detail of a single case. For this an investigation on 

 the spot is necessaiy, and as will appear from the full paper, I have 

 not been able to find much that is new in this direction. 



What was hitherto known about the ovules of Podostemaceae we 

 owe almost exclusively to Warming. As was said above, this author 

 described in detail the lirst development of the ovules of Minopsis 

 Weddelliana Tal, and it was only owing to the want of the exact 

 stages, that the meaning of certain organs did not become clear to 

 him. The development proper of the embryo-sac was completely 

 left out of account, but the development of the embryo of this 

 plant, beginning with the two-celled stage, was treated very thoroughly. 

 It is quite clear from his letter-press and from his figures, that the 

 whole development takes place in the same way as in the species 

 examined by myself. The same can be said of the other cases, in 

 which he has stated or figured something regarding the ovules of 

 Podostemaceae namely Castelnavia princeps Tux, et Wedd.^) Hydro- 

 hryum oUvaceum Gardn. ^) and Tristicha hypnoides Spreng ^). On the 

 last named Cario ■*) had already made observations which seemed 

 to indicate an agreement with the other Podostemaceae as regards 

 the development of the ovule. This is of some little importance, 

 because this plant deviates in the structure of its flowers from the 

 majority of the species of the order. If the development of the 

 ovule here corresponds to what I found in the species examined 

 by me this agreement constitutes an additional reason for supposing, 

 that the order is extremely uniform in its embryogeny, in which it 

 differs so widelj^ from the other Angiosperms. I have already 



1) Warming, I.e. Plate XIV. Fig. 9-21. 



2) Warming, Ibid. 6 Raekke, Nat. og math. Afd. VII. 4. 1891, p. 37, fig. 34. 



3) Warming, Ibid. 6 Raekke, Nat. og math. Afd. IX. 2. 1899. p. 113, fig. 6. 



4) R. Cario. Anatomische Untersuchung von Tristicha hypnoides Spreng. Botan 

 Zeitung. 1881 S. 73, Taf. I. Fig, 20—24. 



