APOGAMOUS FERNS. EVOLUTION OF THE SEPARATE SPECIES 



species are unfortunately so rare that I have not yet seen this type of meiosis, in spite of 

 annual fixations made for the purpose over many years. The possible origin of the 

 species is therefore at present unknown, since the chromosome number (90) is unlike 



Fig. 189. Meiosis in Dryopteris atrata (Wallich) Ching. a. Two mother cells surrounded by tapetum 

 from a sixteen-celled sporangium in a section showing irregular meiotic figures composed largely 

 of unpaired chromosomes, x 1000. b. Spread metaphase from an eight-celled sporangium in 

 balsam after acetocarmine. x 1500. For explanatory diagram see Fig. 190. 'n'-c. 122 = 

 probably 123. 



P^l ^* 



D. atra/^a 



'/?"= /^3 



Fig. 190. Explanatory diagram to Fig. 189^). x 2000. 



that of any of the other genera with which Phegopteris has from time to time been classed 

 and there is therefore as yet no clue to its nearest affinities. 



Somewhat similar uncertainty hangs over the genus Pellaea, of which one species, 

 P. atropurpurea (L.) Link, has been available to me from spores collected wild in Cali- 



184 



