336 CONCLUDING REMARKS Chap. Vlli 



by no means the case; for various parts haye been 

 specially modified, 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 

 Specularia modified into a perfectly closed tympanum, 

 and the sheath of Monochoria modified into a closed 

 sack, — the excessively thin coats of the pollen-grains, 

 — the anthers not being all equally aborted, and other 

 such cases. Moreover Mr. 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 Specularia, the glands on the 

 calyx of the Malpighiaceae, 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 odoraia. We here see, as 

 throughout nature, that as soon as any part or 

 character becomes superfluous it tends sooner or later 

 to disappear. 



Auother peculiarity in these flowers is that tl'.a 



