19 1 7l COLE—POLLEN OF ROSA 121 





In the second group there are 3 phenhybrids and 3 garden 

 varieties probably of hybrid origin though not so designated. The 

 remaining 14 are crypthybrids, several of which are treated as 

 species in standard systematic works; as for example, R. blanda 

 with 20 per cent of its pollen grains abortive, and R. rubiginosa with 

 f pollen almost completely undeveloped. 



In the third and last group I find 3 phenhybrids; one natural 

 hybrid of known parentage, R. alba; two recognized hybrids, 

 R. rubiginosa regarded as derived from R. canina, and R. damascena 

 which is allied to R. centifolia and parent with R. indica of "hybrid 

 perpetual roses"; and two garden varieties of R. rugosa which are 

 also of recognized hybrid origin. The remaining 12 of this group 

 are crypthybrids. 



• These crypthybrids of Rosa are particularly interesting in con- 

 nection with the several theories of the origin of species. We 

 know that they are common not only in the Rosaceae, but, as has 

 been shown to be probable, also in the Onagraceae and other 

 families of the angiosperms. Such forms, though recognized 

 I* as species, obviously cannot rank with pure species in the sense in 



which that term is applied to gymnosperms, etc., in evolutionary 

 discussions; for, as Jeffrey has recently stated (see footnote 6), 

 "The conduct of such forms is conditioned more or less by their 

 mixed blood." 



In this connection it is interesting to note the conditions pre- 

 sented by Oenothera Lamarckiana and other species of the genus 

 as described by DeVries and other authors. Here we have, as is 

 the case in Rosa, a considerable degree of variability accompanied 

 by a large amount of pollen sterility. Upon Oenothera and forms 

 manifesting similar peculiarities DeVries has mainly based his 

 mutation hypothesis. 



To go back to the original question, are new species the result 

 of gradual changes or sudden leaps ? The Darwinian hypothesis, 

 as has been pointed out, is in large measure supported by the 

 species of Pinus. But, as I have shown, the term species when 

 used of Pinus has an altogether different significance from that 

 which it has when used of Rosa; and consequently, the problem of 

 evolution as presented by the species of Rosa must be an entire ly 



f 



• 



