566 SCIEXCE PROGRESS. 



above and below the Tosa Falls, the plant abounds in both 

 these two forms, the smooth being on the whole the more 

 abundant. Now between these two there are various inter- 

 mediate forms making a complete series connecting them. 

 But though the degree of hairiness varies, and the degree 

 of smoothness varies, the immense majority of plants in the 

 locality can be referred unhesitatingly either to the hairy 

 class or to the smooth. Plants which are so intermediate in 

 character as to cause the observer any doubt as to the class 

 to which they belong are decidedly scarce. Owing to the 

 fact that the plants increase much by runners, forming 

 new crowns which afterwards separate, it is impossible to say 

 which should be counted as " individuals," and hence it is 

 not easy to see how a reliable numerical measure of the 

 discontinuity can be obtained, but that the fact is substan- 

 tially as stated there is no doubt. 



The question then arises, how is it that these two distinct 

 varieties can exist side by side, exposed to the visits of in- 

 sects, without regressing to the mean form, which, as was 

 stated, is comparatively scarce ? To determine this Miss 

 Saunders made artificial crossings of the two varieties in 

 the Cambridge Botanic Gardens. The mongrel seedlings, 

 judged by their first few leaves, consisted of some hairy, 

 some smooth, and a large number of various intermediate 

 forms. But it was found that as these seedlings grew older, 

 while the hairy continued to put up leaves which were hairy, 

 the intermediates in their later leaves turned to smooths. 

 The original smooths also to some extent became smoother. 

 When, therefore, the well-grown mongrel plants are 

 examined they present just the same appearance of discon- 

 tinuity which the wild plants at the Tosa Falls do. This 

 discontinuity is, therefore, the outward sign of the fact that 

 in hereditv the two characters of smoothness and hairiness 

 do not completely blend, and the offspring do not regress 

 to one mean form, but to two distinct forms. The variety, 

 in short, is not "swamped by intercrossing". 



Which may be the older form we will not venture to 

 discuss. It is, however, of no small interest to note that 

 Miss Saunders found that the smooth plants sufiered far 



