Chap. VIII. ON CLEISTOGAMIC FLOWERS. 



335 



i 



so as to aid in the self -fertilisation of the flowers, and 

 as a protection to the pollen; for instance, the hook- 



* 



shaped pistil in Viola and in some other genera, by 

 which the stigma is brought close to the fertile anthers, 

 •the rudimentary corolla of Speeularia modified into 

 a perfectly closed tympanum, and the sheath of Mono- 

 choria modified into a closed sack,— 



coats of the pollen-grains, 



the excessively thin 

 the anthers not being all 



Moreover Mr. 



equally aborted, and other such cases. 

 Bennett has shown that the buds of the cleistogamic and 

 perfect flowers of Impatiens differ at a very early period 

 of growth. 



The degree to which many of, the most important 

 organs in these degraded flowers have been reduced 

 or even wholly obliterated, is one of their most re- 

 markable peculiarities, reminding us of many parasitic 

 animals. In some cases only a single anther is left, 

 and this contains but few pollen-grains of diminished 

 size; in other cases the stigma has disappeared, 

 leaving a simple open passage into the ovarium. It 

 is also interesting to note the complete loss of trifling 

 points in the structure or functions of certain parts, 

 which though of service to the perfect flowers, are of 

 none to the cleistogamic; for instance, the collecting 

 hairs on the pistil of Speeularia, the glands on the 

 calyx of the Malpighiacea?, the nectar-secreting ap- 

 pendages to the lower stamens of Viola, the secretion 

 of nectar by other parts, the emission of a sweet odour, 

 and apparently the elasticity of the valves in the 

 buried capsules of Viola odorata. We here see, as 

 throughout nature, that as soon as any part or char- 

 acter becomes superfluous it tends sooner or later to 



disappear. 



Another peculiarity in these flowers is that the 

 pollen-grains generally emit their tubes whilst still 





