No. 591] HYBRIDISM IN AN GIO SPERMS 141 



in genera with often highly sterile species, such as Rubus, 

 the species which are isolated for any reason from the 

 rest have either perfect pollen or manifest a much less 

 marked degree of sterility. An objection urged by De 

 Vries to gametic degeneracy as a criterion of hybridism 

 needs apparently only to be stated to supply its own refu- 

 tation. The distinguished plant physiologist of Amster- 

 dam, in a recent article in which he criticizes the writer's 



attitude in regard to the intimate relation between de- 

 fective pollen, hybridization and so-called mutation, some- 

 what superciliously, states that the degeneracy of spores 

 in connection with the development of the megaspores of 

 the heterosporous vascular Cryptogams (and one might 

 add the seed plants as well) might with equal validity be 

 regarded as evidence of hybridism in the megasporic 

 sporangia. One has only to carry De Vries 's argument 

 to its logical conclusion to prove its entire fallacy. Since 

 microsporic sporangia (in which there is no spore degen- 

 eration apart from hybridism) and megasporic sporangia 

 occur ordinarily or at least primitively on the same plant, 



