44 HETEKOSTYLED DIMOEPHIC PLANTS. Chap. I. 



access of insects, and they did not produce a single seed. Mr. 

 Scott protected six plants of both forms, and found them ex- 

 cessively sterile. The pistil of the long-styled form stands so 

 high above the anthers, that it is scarcely possible that pollen 

 should reach the stigma without some aid; and one of Mr. 

 Scott's long-styled plants which yielded a few seeds (only 18 ia 

 number) was infested by aphides, and he does not doubt that 

 these had imperfectly fertilised it. 



I tried a few experiments by reciprocally fertilising the two 

 forms in the same manner as before, but my plants were im- 

 healthy, so I will give, in a condensed fonn, the results of Mr, 

 Scott's experiments. For fuller particulars with respect to this 

 and the five following species, the paper lately referred to may 

 be consulted. In each case the fertility of the two legitimate 

 unions, -taken together, is compared with that of the two ille- 

 gitimate unions together, by the same two standards as before, 

 namely, by the proportional number of flowers which pro- 

 duced good capsules, and by the average number of seeds per 

 capsule. The fertility of the legitimate unions is always taken 

 at 100. 



By the first standard, the fertility of the two legitimate unions 

 of the auricula is to that of the two illegitimate unions as 100 

 to 80 ; and by the second standard as 100 to 15. 



Peimula Sikkimensis. 



According to Mr. Scott the pistil of the long-styled form is 

 fuUy four times as long as that of the short-styled, but their 

 stigmas are nearly alike in shape and roughness. The stamens 

 do not differ so much in relative length as the pistils. The pollen- 

 grains differ in a marked manner in the two forms ; " those oi 

 the long-styled plants are sharply triquetrous, smaller, and more 

 transparent than those of the short-styled, which are of a bluntly 

 triangular form." The fertility of the two legitimate unions to 

 that of the two illegitimate unions is by the first standard as 

 100 to 95, and by the second standard as 100 to 31. 



Peimtjla coetusoides. 



The pistil of the long-styled form is about thrice as long as 

 that of the short-styled, the Stigma being double as long and 

 covered with much longer papilla. The pollen-grains of the short* 



