42 



and as robustly as P. glaucum, it is an exact replica on that 

 large scale of the comparatively small P. v. elegantissinmm, 

 and is, moreover, nearly hardy. The evidence is farther 

 strengthened by the fact that P. v. elegantissimum is polymor- 

 phic, bearing several distinct types of fronds, viz. normal, very 

 finely dissected, and intermediate, i.e. more coarsely divided, 

 and the hybrid does precisely the same, even to the fact 

 that one and the same frond may display all three characters 

 in the most wayward way conceivable. 



Among existing varieties of British Ferns there is a con- 

 siderable number of undoubted crosses. One form of 

 PolysticJmni angulare (P. ang. polydactyhim) appears to possess 

 an extraordinary faculty of imparting its polydactylo2is 

 character to any Polystichnm it is sown with. There are 

 scores of other varieties which have thus been rendered 

 polydactylous by conjoined sowing with this fern, and the fact 

 that the new character is due to this crossing and not 

 spontaneous, is practically proved by a parental defect 

 common to all the offspring, viz., pinnae here and there 

 which are not so characterized. I have seen a very large 

 number, and never found aa exception to this. Others 

 might be cited, but these are sufficient to prove beyond all 

 doubt that cross fertilization does occur, both between 

 species and varieties. Given, indeed, a somewhat dense 

 mass of prothalli of two kinds, and a flooding when they are 

 mature, the water must be pervaded by the fertilizing 

 antherozoids, which can thus find their way to alien prothalli 

 and so fertilize them. Given, too, a purposed crossing with 

 two distinct forms, and a percentage of progeny showing 

 both types conjoined, and we are certainly entitled to 

 attribute such result to cross fertilization, though we may 

 not have been able, as with flowers, to bring the two dis- 

 tinct reproductive elements together manually, as can be 

 done with pollen grains. 



C. T. D. 



