148 STERILITY FROM CHANGED CONDITIONS. Chap. X\'1U. 



resists the severest frosts, and I have seen seeds gathered from pods 

 "which had been covered with snow during three weeks.**^ Berberis 

 wallichii, from the hot Khasia range in India, is uninjured by our 

 sharpest frosts, and ripens its fruit under our cool summers. 

 Nevertheless, I presume we must attribute to change of climate the 

 sterility of many foreign plants ; thus, the Persian and Chinese 

 lilacs {Syringa persica and chinensis), though perfectly hardy 

 here, never produce a seed ; the common lilac {S. vulgaris) seeds 

 with us moderately well, but in parts of Germany the capsules 

 never contain seed.^* Some few of the cases, given in the last 

 chapter, of self-impotent plants, might have been here introduced, 

 as their state seems due to the conditions to wliich they have been 

 subjected. 



The liability of plants to be affected in their fertility by slightly 

 changed conditions is the more remarkable, as the pollen when 

 once in process of formation is not easily injured ; a plant may be 

 transplanted, or a branch with flower-buds be cut olf and placed in 

 water, and the pollen will be matured. Pollen, also, when 

 once mature, may be kept for weeks or even months.^^ The female 

 organs are more sensitive, for Gartner ^^ found that dicotyledonous 

 plants, when carefully removed so that they did not in the least 

 flag, could seldom be fertilised ; this occurred even with potted 

 plants if the roots had grown out of the hole at the bottom. In 

 some few cases, however, as with Digitalis, transplantation did not 

 prevent fertilisation; and according to the testimony of Mawz, 

 Brassica rapa, when pulled up by its roots and placed in water, 

 ripened its seed. Flower-stems of several monocotyledonous plants 

 uhen cut off and placed in water likewise produce seed. But in 

 these cases I presume that the flowers had been already fertilised, 

 for Herbert ^' found with the Crocus that the plants might be re- 

 moved or mutilated after the act of fertilisation, and would still 

 perfect their seeds; but that, if transplanted before being fertilised, 

 the application of pollen was powerless. 



Plants which have been long cultivated can generally endure 

 with undiminished fertility various and great changes ; but not in 

 most cases so great a change of climate as domesticated animals. 

 It is remarkable that many plants under these circumstances are 

 so much affected that the proportion and the nature of their che- 

 mical ingredients are modified, yet their fertility is unimpaired. 

 Thus, as Dr. Falconer informs me, there is a great difference in the 

 character of the fibre in hemp, in the quantity of oil in the seed of 



*^ Dr. Herbert, ' Amaryllidaceas,* ' La Variabilite des Especes,' 1868, p. 



p. 176, 155, 



** Gartner, ' Beitrage zur Kennt- *^ * Beitrage zur Kenntniss,' &c., s. 



Diss,' &c., s. 560, 564. 252, 333. 



85 * Gardener's Chronicle,* 1844, p. ^7 i Journal of Hort. Soc.,* voL ii., 



215 ; 1850, p. 470. Faivre gives a 1847, p. 83. 

 good resume on this subject in his 



