166 



STERILITY. 



Chap. XVIII. 



is 





plants are eminently liable to this affection also seems to show that it 

 in some manner caused by their unnatural treatment. In some instances* 

 as with Silene, Gartner's view seems the most probable, namely, that it is 

 caused by an inherent tendency in the species to become dioecious. I can 

 add another cause, namely, the illegitimate unions of reciprocally dimorphic 

 or trimorphic plants, for I have observed seedlings of three species of 

 Primula and of Lythrum salicaria, which had been raised from plants 

 illegitimately fertilised by their own-form pollen, with some or all their 

 anthers in a contabescent state. There is perhaps an additional cause 

 namely, self-fertilisation ; for many plants of Dianthus and Lobelia, which 

 had been raised from self-fertilised seeds, had their anthers in this state ■ 

 but these instances are not conclusive, as both genera are liable from other 

 causes to this affection. 



Cases of an opposite nature likewise occur, namely, plants with the 

 female organs struck with sterility, whilst the male organs remain perfect. 

 Dianthus Japonicus, a Passiflora, and Nicotiana, have been described by 

 Gartner 85 as being in this unusual condition. 



Monstrosities as a cause of Sterility. — Great deviations of structure, even 

 when the reproductive organs themselves are not seriously affected, some- 

 times cause plants to become sterile. But in other cases plants may 

 become monstrous to an extreme degree and yet retain their full fertility. 

 Gallesio, who certainly had great experience, 86 often attributes sterility to 

 this cause ; but it may be suspected that in some of his cases sterility was 

 the cause, and not the result, of the monstrous growths. The curious 

 St. Valery apple, although it bears fruit, rarely produces seed. The 

 wonderfully anomalous flowers of Begonia frigida, formerly described, 

 though they appear fit for fructification, are sterile. 87 Species of Pri- 

 mulae, in which the calyx is brightly coloured, are said 88 to be often 

 sterile, though I have known them to be fertile. On the other hand, 

 Verlot gives several cases of proliferous flowers which can be propa- 

 gated by seed. This was the case with a poppy, which had become 

 monopetalous by the union of its petals. 89 Another extraordinary poppy, 

 with the stamens replaced by numerous small supplementary capsules, 

 likewise reproduces itself by seed. This has also occurred with a plant of 

 Saxifraga geum, in which a series of adventitious carpels, bearing ovules 

 on their margins, had been developed between the stamens and the normal 

 carpels. 90 Lastly, with respect to peloric flowers, which depart wonder- 

 fully from the natural structure, — those of Linaria vulgaris seem generally 

 to be more or less sterile, whilst those before described of Antirrhinum 

 majus, when artificially fertilised with their own pollen, are perfectly 



85 ' Bastarderzeugung/ s. 356. in the ' Phytologist/ vol. ii. p. 483. 



86 ' Teoria della Kiproduzione/ 1816, Prof. Harvey, on the authority of Mr- 

 p. 84; < Traite du Citrus,' 1811, p. 67. Andrews, who discovered the plant, 



8 7 Mr. C. W. Crocker, in ' Gard. informed me that this monstrosity could 



Chronicle/ 1861, p. 1092. be propagated by seed. With respect to 



88 Verlot, ' Des Varieties/ 1865, p. 80. the poppy, see Prof. Goeppert, as quoted 



89 Verlot, idem, p. 88. in < Journal of Horticulture/ July lst ' 



90 Prof. Allman, Brit. Assoc, quoted 1863, p. 171. 



