* 



r 



191 7] COLE— POLLEN OF ROSA 119 



absence." Among the gymnosperms he examined Cycadales, 

 Ginkgoales, Coniferales, and Gnetales, and found "a single species 

 of Abies with evidence of abortive pollen grains of hybrid origin." 



The photomicrographs of Lycopodium complanatum and Pin us 

 divaricata (figs, i, 2) show clearly the morphological condition typi- 

 cal in both genera, fertile spores uncontaminated by any abnormal, 

 sterile grains. Jeffrey states that "the genus Pinus is very old 

 and its species accordingly very distinct"; and he has not yet 

 found "the slightest evidence of hybridization here or in other 

 numerous and widely distributed species of conifers, other than the 

 Abies mentioned above." 



In the angiosperms, on the contrary, hybridism as a condition 

 widespread in nature is commonly recognized. For example, in this 

 country and in Europe systematic botanists agree that hybridism 

 is extremely common as a natural condition in certain genera of 

 the Rosaceae. Brainerd has shown that a great many "natural 

 hybrids" of Rosa and Rubus, occur; and Jeffrey 7 in a recent 

 article says as follows : 



Not only are certain of the Rosaceae recognizable as hybrids on account 



f of their transitional external features of organization, Mendelian phenomena, 



J etc., but certain others which have not revealed themselves as hybrids in these 



J ways are clearly such as a result of a study of their spores Taking 



j morphological features into account, as well as the data of the systematic 



J botanists, there are three kinds of individuals; pure species, recognized species 



I with pollen showing they are concealed hybrids or crypthybrids, and recog- 



I nized hybrids or phenhybrids. 



! These 3 classes, typical of many angiospermous genera, make 





it difficult to determine 



form a species 



therefore, the term 

 from that in which 



lower vascular plants. Clearly crypthybrids should not be species 



same 



morphologically normal genera. But they are generally admitted 

 by the systematist as good species because of their relative con- 

 stancy and the absence of observed intergrading types, though 

 the morphological conditions are undoubtedly those of hybrids. 



7 Jeffrey, E. C, Spore conditions in hybrids and the mutation hypothesis of 



DeVries. Bot. Gaz. 58:322-336. pis. 22-25. 1914. 



