68 HYBRID PRIMULAS, Chap. IL 



have like distinct species, for they are far from 

 being mutually fertile. Gartner * crossed 27 flowers 

 of P. vulgaris with pollen of P. veris, and obtained 

 19 capsules; but these did not contain any good 

 seed. He also crossed 21 flowers of P. veris with 

 pollen of P. vulgaris; and now he got only five 

 capsules, containing seed in a still less perfect 

 condition. Gartner knew nothing about hetero- 

 stylism; and his complete failure may perhaps be 

 accounted for by his having crossed together the 

 same forms of- the cowslip and primrose; for such 

 crosses would have been of an illegitimate as well as 

 of a hybrid nature, and this would have increased 

 their sterility. My trials were rather more fortunate. 

 Twenty-one flowers, consisting of both forms of the 

 cowslip and primrose, were intercrossed legitimately, 

 and yielded seven capsules (i. e. 33 per cent.), contain- 

 ing on an average 42 seeds; some of these seeds, 

 however, were so poor that they probably would not have 

 germinated. Twenty-one flowers on the same cowslip 

 and primrose plants were also intercrossed illegiti- 

 mately, and they likewise yielded seven capsules (or 

 33 per cent.), but these contained on an average only 

 13 good and bad seeds. I should, however, state that 

 some of the above flowers of the primrose were fertilised 

 with pollen from the polyanthus, which is certainly a 

 variety of the cowslip, as may be inferred from the per- 

 fect fertility inter se of the crossed offspring from these 

 two plants, t To show how sterile these hybrid unions 



*'Bastarderzeugung,' 1849, p. ciently numerous. The degree of 



721. infertility of a cross is liable to 



t Mr. Scott has discussed the much fluctuation. Pollen from 

 nature of the polyanthus (' Proc. the cowslip at first appears rather 

 Linn. Soo. Bot.,' viii., 1864, p. more efficient on the primrose than 

 103), and arrives at a different that of the polyanthus; for 18 

 conclusion ; but I do not think flowers of both forms of the prim- 

 that his experiments were suffi- rose, fertilised legitimately and 



