APOGAMOUS FERNS. EVOLUTION OF THE SEPARATE SPECIES 



the cells shown in Fig. 1 83 a and b, which relate to C. falcatum and the wild C. Fortunei 

 from China respectively, the number is 'not less than 122 nor more than 123'. In the 

 cell of Fig. 183 c of wild C. caryotideum from Uganda the number is exactly 123. 



The significance of this chromosome number is considerable. It is about twice that 

 recorded by Allen, but it is not a tetraploid and there seems httle doubt, especially in 

 view of the results obtained by reinvestigating Wisconsin material (Figs. i8ia, 182 a), 



Fig. 181. Cyrtomium chromosome counts from section, a, b, c. Three different focal levels of a plate 

 of chromosomes in a root of the Wisconsin plant (see text), x 1500. For explanatory diagram see 

 Fig. 182a. d. Meiosis in C. falcatum (L.f.) Presl, plate of chromosomes slightly dismembered by 

 pressure, x 2000. For explanatory diagram see Fig. 1826. e. Mitosis in a root of C. /a/catom var. 

 Rockfordii from Kew. x 1000. For explanatory diagram see Fig. 182 c. 



that Miss Allen's estimate must have been due to technical error and not to genetical 

 diiTerence of her specimen. 



The obvious interpretation of the actual number found is that it is that of a triploid, 

 since the monoploid number 41 is known to characterize a number of very closely 

 related genera, notably Dryopteris and Polystichum. This interpretation is to some extent 

 confirmed by the evidence from chromosome pairing in the sixteen-celled sporangia. 

 Trivalents are certainly present (Fig. 185), together with pairs and a large number of 

 univalents. Trivalents are not in themselves diagnostic of triploidy if present in small 

 numbers, and if the subject is not an autotriploid, nevertheless, they are some confirma- 

 tion of the status of the parent plant if this had been diagnosed from other evidence. 



179 



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