Chap. XVII. SELF-IMPOTENT PLANTS. 137 



garden plants of Verbascum phoeniceum, which bore during two years many 

 flowers ; these he successfully fertilised by the pollen of no less than four 

 distinct species, but they produced not a seed with their own apparently 

 good pollen; subsequently these same plants, and others raised from 

 seed, assumed a strangely fluctuating condition, being temporarily sterile 

 on the male or female side, or on both sides, and sometimes fertile on 

 both sides; but two of the plants were perfectly fertile throughout the 

 summer. 



It appears 67 that certain flowers on certain plants of Lilium candidum 

 can be fertilised more easily by pollen from a distinct individual than by 

 their own. So, again, with the varieties of the potato. Tinzmann, 68 who 

 made many trials with this plant, says that pollen from another variety 

 sometimes " exerts a powerful influence, and I have found sorts of potatoes 

 " which would not bear seed from impregnation with the pollen of their 

 " own flowers, would bear it when impregnated with other pollen." It 

 does not, however, appear to have been proved that the pollen which failed 

 to act on the flower's own stigma was in itself good. 



In the genus Passiflora it has long been known that several species do 

 not produce fruit, unless fertilised by pollen taken from distinct species : 

 thus, Mr. Mowbray 69 found that he could not get fruit from P. alata and 

 racemosa except by reciprocally fertilising them with each other's pollen. 

 Similar facts have been observed in Germany and France ; 70 and I have 

 received two authentic accounts of P. quadrangular is, which never pro- 

 duced fruit with* its own pollen, but would do so freely when fertilised in 

 one case with the pollen of P. coerulea, and in another case with that of 

 P. edulis. So again, with respect to P. laurifolia, a cultivator of much 

 experience has recently remarked 71 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 Mr. Scott: 72 plants of Passiflora racemosa, coerulea, and 

 alata flowered profusely during many years in the Botanic Gardens of 

 Edinburgh, and, though repeatedly fertilised by Mr. Scott and by others 

 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. 

 But in the case of P. coerulea, three plants, two of which grew in the 

 Botanic Gardens, were all rendered fertile, merely by impregnating the one 

 with pollen of the other. The same result was attained in the same 

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

 self-sterile species have been mentioned, it may be stated that in the case 

 of P. gracilis, which is an annual, the flowers are nearly as fertile with their 

 own pollen as with that from a distinct plant ; thus sixteen flowers sponta- 



67 



Duvernoy, quoted by Gartner, 70 p ro f. Lecoq, ' De la Fecondation,' 



' Bastarderzeugung,' s. 334. 1845, p. 70 ; Gartner, ' Bastarderzeug- 



68 ' Gardener's Chronicle,' 1846, p. ung ' s. 64. 



183 - 7 °'' Gardener's Cliron.,' 1866, p. 1068. 



OT 'Transact. Hort. Soc.,' vol. vii., 72 'Journal of Proc. of Linn. Soc.,' 



1830, p. 95. vol, viiij 1864j p 1168 . 



