Chap. XVII. SELF-IMPOTENT PLANTS. 119 



other cases this species fruited freely when fertilised with its own 

 pollen ; and the writer in one case attributed the favourable result 

 to the temperature of the house having been raised from 5° to 10° 

 Fahr. above the former temperature, after the flowers were fertilised. 79 

 With respect to P. laurifolia, a cultivator of much experience has 

 recently remarked 80 that the flowers "must be fertilised with the 

 pollen of P. coerulea, or of some other common kind, as their own 

 pollen will not fertilise them." But the fullest details on this 

 subject have been given by Messrs. Scott and Eobertson Munro : 81 

 plants of Passiflora racemosa, coerulea, and alata flowered profusely 

 during many years in the Botanic Gardens of Edinburgh, and, 

 though repeatedly fertilised with their own pollen, never produced 

 any seed ; yet this occurred at once with all three species when they 

 were crossed together in various ways. In the case of P. coerulea 

 three plants, two of which grew in the Botanic Gardens, were all 

 rendered fertile, merely by impregnating each with pollen of one of 

 the others. The same result was attained in the same manner with 

 P. alata, but with only one plant out of three. As so many self- 

 sterile species of Passiflora have been mentioned, it should be 

 stated that the flowers of the annual P. gracilis are nearly as fertile 

 with their own pollen as with that from a distinct plant; thus 

 sixteen flowers spontaneously self-fertilised produced fruit, each 

 containing on an average 21*3 seed, whilst fruit from fourteen 

 crossed flowers contained 241 seed. 



Beturning to P. alata, I have received (1866) some interesting- 

 details from Mr. Eobertson Munro. Three plants, including one in 

 England, have already been mentioned which were inveterately 

 self-sterile, and Mr. Munro informs me of several others which, 

 after repeated trials during many years, have been found in the 

 same predicament. At some other places, however, this species 

 fruits readily when fertilised with its own pollen. At Taymouth 

 Castle there is a plant which was formerly grafted by Mr. Donaldson 

 on a distinct species, name unknown, and ever since the operation 

 it has produced fruit in abundance by its own pollen; so that this 

 small and unnatural change in the state of this plant has restored 

 its self- fertility ! Some of the seedlings from the Taymouth Castle 

 plant were found to be not only sterile with their own pollen, but 

 with each other's pollen, and with the pollen of distinct species. 

 Pollen from the Taymouth plant failed to fertilise certain plants of the 

 same species, but was successful on one plant in the Edinburgh 

 Botanic Gardens. Seedlings were raised from this latter union, and 

 some of their flowers were fertilised by Mr. Munro with their own 

 pollen ; but they were found to be as self-impotent as the mother- 

 plant had always proved, except when fertilised by the grafted 



' 9 < Gard. Chron.,' 1868, p. 1341. vol. viii., 1864, p. 1168. Mr. Robert- 



80 ' Gardener's Chron.,' 1866, p. son Munro, in ' Trans. Bot. Soo. ; of 

 1068. . Edinburgh, vol. ix. p. 399. 



81 ' Journal of Proc. of Linn. Soc.,' 



