THE ANCIENT FERNS 



and believed to have come in the first instance from South America, are 0. gracilis Hort. 

 and 0. palustris Hort.* (Fig. 276), the first a hardy deciduous plant and the second a 

 stove evergreen. Their chromosomes are visible in Fig. 2771^ and d. Lastly, O.javanica 



J 





^' ^ft. 



> 



% 



A 



0^ 



1» 



« 



Vr 



\^ V 



5 



^ •^1% ■ '*^ 





Fig. 278. Meiosis in Todea and Leptopteris, in permanent acetocarmine. x 1000. ;z=22 throughout. 

 a. Todea barbara (L.) Moore, b. Leptopteris Frazeri (Hk. et Grev.) PresL c. L. hymenophylloides 

 (A. Rich.) PresL d. L. siiperba (Col.) PresL 



BL, the most genuinely tropical species, will be found in Fig. 277^. It is obvious at a 

 glance that all these species are very similar cytologically. All have a chromosome 

 number which is identical with that of 0. regalis, namely, n = 22. The only detectable 

 difference to the eye is indeed the slightly smaller chromosome size in the last 



* The origin of this well-known horticultural plant is somewhat obscure, since it seems to have been 

 confused at a very early date with 0. gracilis Link with which it is not identical. If it does not come from 

 South America its origin is unknown. 



278 



