Chap. I. SUMMARY ON PRIMULA. 45 



standard as 100 to 74, and by the second standard as 100 

 to 66. 



Primula involucrata. 



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

 long as that of the short-styled ; the stigma of the former is 

 globular and closely beset with papillae, whilst that of the 

 short-styled is smooth and depressed on the apex. The 

 pollen-grains of the two forms differ in size and trans- 

 parency as before, but not in shape. The fertility of the 

 two legitimate to that of the two illegitimate unions is by 

 the first standard as 100 to 72 ; and by the second standard 

 as 100 to 47. 



Primula farinosa. 



According to Mr. Scott, the pistil of the long-styled 

 form is only about twice as long as that of the short-styled. 

 The stigmas of the two forms differ but little in shape. The 

 pollen-grains differ in the usual manner in size, but not in 

 form. The fertility of the two legitimate to that of the two 

 illegitimate unions is by the first standard as 100 to 71, and 

 by the second standard as 100 to 44. 



Summary on the foregoing heterostyled species of 

 Primula. — The fertility of the long and short-styled 

 plants of the above species of Primula, when the two 

 forms are fertilised legitimately, and illegitimately with 

 pollen of the same form taken from a distinct plant, 

 has now been given. The results are seen in the fol- 

 lowing table; the fertility being judged by two stand- 

 ards, namely, by that of the proportional number of 

 flowers which yielded capsules, and by that of the aver- 

 age number of seeds per capsule. But for full accu- 

 racy many more observations, under varied conditions, 

 would be requisite. 



With plants of all kinds some flowers generally fail 

 to produce capsules, from various accidental causes; 

 but this source of error has been eliminated, as far as 



