APOGAMOUS FERNS. EVOLUTION OF THE SEPARATE SPECIES 



Steil's was also of botanic garden origin it is possible that the two are identical. This 

 supposition is not affected by the change of name, which is quite recent* (Ching, 1933). 



a be 



Fig. 185. Details of chromosome pairing in sixteen-celled sporangia oi Cyrtomium Fortunei J.Sm., from 

 a section, x 3000. a. Pachytene showing a trivalent. b. Diakinesis showing trivalents. c. Meta- 

 phase showing a trivalent, a univalent and other groups. 



Fig. 186. Dryopteris atrata (Wallich) Ching. Part of a dried frond 

 of the plant used. Natural size. 



Some of the sporangial peculiarities of Dryopteris atrata have already been mentioned 

 in a previous chapter, and it only remains to add such details as may be of evolutionary 

 importance. The most significant detail is again the chromosome number. As in the 

 case of Cyrtomium I differ considerably from previous investigators, in this case Steil 

 (19 19) and Andersson and Gairdner (1930), for reasons which I can only interpret as 



* The change of name results from a splitting of the former collective species Nephrodium hirtipes into 

 two, the Chinese portion now constituting Dryopteris atrata and the Indian portion retaining the epithet 

 hirtipes. On comparison with Ching's diagnoses (1933), the botanic garden form, the origin of which is 

 unknown, was found to conform to the Chinese variant. The labels were emended in consequence, though 

 the plant is the same as that formerly disseminated under the older name. 



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