46 University of California Publications in Botany [Vol. 6 



often of normal size with the pollen imperfect, the pollen grains often 

 enlarged and stuffed with innumerable spore-like bodies, the nature 

 of which has not been determined. The healthy pollen is of very 

 unequal size especially in certain plants. 



In this species, self-fertilization is the rule in normal plants, the 

 anthers opening a day before the bud, and in my observation the 

 stigma always showing pollen at the time of the opening of the flower, 

 but from failure of viable pollen, crossing is probably not rare. 

 Judging from the grouping of forms and their spreading from parent 

 localities it seems probable that most of the forms here described come 

 true from seed. 



Little attention has been given to disease forms in Oe. ovata, partly 

 from lack of time, partly because its low growth and hidden fruit make 

 its study difficult. Fasciation occasionally occurs, and is, so far as my 

 experience goes, always associated with abundance of aphis. Double 

 forms are rare and usually are produced by transformation of the 

 stamens. 



It will be apparent from the foregoing that there are quite as 

 many "elementary species" in Oenothera ovata as in the better known 

 Oe. hiennis-Lamarckiana group. In this connection I wish to call 

 attention to some remarks by De Vries^ that seem to be overlooked by 

 many systematists : 



Species is a word which always has had a double meaning. One of them 

 is the systematic species, which is the unit of our system. But these units are 

 not at all undivisible. . . . Today the vast majority of the old systematic species 

 are known to consist of minor units. These minor entities are called varieties 

 in systematic works. However, there are many objections to this usage. . . 

 Some of these varieties are in reality as good as species, and have been 

 "elevated," as it is called, by some writers, to this rank. This conception of 

 the elementary species would be quite justifiable, and would at once get rid of 

 all difficulties, were it not for one practical obstacle. The number of the species 

 in all genera would be doubled and tripled, and as these numbers are already 

 cumbersome in many cases, the distinction of the native species of any given 

 country would lose most of its charm and interest. 



In order to meet this difficulty we must recognize two sorts of species. The 

 systematic species are the practical units of the systematists and florists, and 

 all friends of wild nature should do their utmost to preserve them as Linnaeus 

 has proposed them. 



3 De Vries, Species and Varieties, Their Origin hy Mutation, i)p. 10-12. 



