4.68 ABORTION. 
the filaments often bemg 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 fertilisation of the ovary ; 
A, 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- 
1 Cited in ‘ Henfrey’s Botanical Gazette,’ i, p. 179. 
