Ko. 640] VARIATION AND HEREDITY IN LUPINUS 437 



matter of some surprise to find that the forms of apricus 

 and pipersmithii which were brought into cultivation 

 did not indicate this to be true. The pinks bred true in 

 both species. Experiments to determine self-pollination 

 by bagging or screening the plants with fine-meshed wire 

 cages showed no diminution in the harvest. Further- 

 more, in the following years different strains grown in 

 adjacent rows showed no sign of crossing. It was then 

 assumed that the same would be true of nanus and flower 

 clusters were bagged in the field for seeds — not to insure 

 selfing, but merely to prevent the seeds from being scat- 

 tered by the explosive dehiscence of the pods. The re- 

 sults were wholly negative, resulting in a failure to 

 secure any seed that year. The appearance of the 

 contents of the paper bags first used led to the supposi- 

 tion that possibly the failure to set seed was due to the 

 bags. Careful experiments were therefore taade the 

 following season by inclosing whole plants in cages of 

 fine screen wire or cheesecloth. In no case did this result 

 in setting seed. It appears, therefore, that nanus is de-- 

 pendent on bees for pollination. On the other hand, cul- 

 tures derived from white-flowered nanus have shown that 

 the bees act in part merely as a mechanical agent, for 

 part of tlie progeny was white and part blue" These 

 results agree well with and serve to explain the greater 

 number of vai'iatit)iis found in nanus. 



Pollen 8terilHi).~li has been maintained by a number 

 of authors at one time or another that variabilitv in 

 nature is very largely a matter of liybridity and that 

 sterile pollen is a more or less certain indication of the 

 hybrid nature of a species (6). Having found two closely 

 related species both variable and in a closely similar 

 manner, it became a matter of interest to study the com- 

 parative sterility of close-pollinated and cross-pollinated 

 species. In order to determine this matter a large num- 

 ber of plants belonging to all the varieties in cultivation 

 at the time in the garden were examined. Mounts of 

 pollen from three different flowers from each plant were 



