468 ABORTION. 



the filaments often -being developed without anthers. 

 Ultimately a deformed and empty perianth alone re- 

 mains. In the ordinary course of things the mouth 

 of the perianth is open, but in some of these malfor- 

 mations it is closed, and when that happens, the effects 

 of atrophy are the more observable in the stamens and 

 pistils. 



The impotence of the pollen in certain atrophied 

 flowers, as noticed by the same observer, is of much 

 interest, especially in reference to the sexual relationship 

 between the different forms in polymorphic flowers as 

 studied by Mr. Darwin. 



A change in direction may also be noted as a common 

 accompaniment of atrophy or suppression ; thus, in a 

 capsule of Veronica Beccabunga, which was one-celled 

 by the abortion of one carpel, the style was lateral 

 instead of terminal. 



As to the causes of these structural deviations butlittle 

 is known ; certain of them have been already alluded to. 

 In some cases atrophy and suppression may be regarded 

 as permanent states of a condition usually transitory, 

 but this is clearly not always the case. Among external 

 causes anything bringing about an enfeebled condition 

 might be supposed to lead to atrophy, or suppression 

 of some parts. 



Gaertner^ attributes the arrested development and 

 fall of flowers to some among the following causes: 

 1. non-application of the pollen of the same variety, 

 and consequent imperfect fertilisation; 2. any con- 

 siderable injury to the calyx, &c. ; 3. destruction of 

 the style or stigma before the fertihsation of the ovary ; 

 4. application to the stigma of imperfect or hetero- 

 geneous pollen or indifferent pulverulent matter ; 5. 

 defective conceptive power in the ovary. 



Abortion of the ovules is considered by the same 



authority to be due to 1. deficiency of heat ; 2. excess 



of moisture ; 3. peculiar formation of the ovary ; 4. 



over-luxuriant development of roots or buds ; 5. pe- 



Cited in ' Henfrey'a Botamcal Gazette,' i, p. 179, 



