RELATIONS OF OVA AND GEMMAE. 201 



development of the ovule without impregnation into a fertile 

 seed, and ordinary gemmation, may probably be ranged 

 what are called viviparous flowers. In these buds are 

 formed within organs having the general character of floral 

 envelopes, where they occupy commonly the position of 

 the ovary in a normal flower. This peculiarity sometimes 

 constitutes a specific or constant character, as in the Poly- 

 gonium mmparum, in which, while the upper bracts of the 

 floral spike bear the sexual flowers, the lower ones bear 

 gemmse, ripening without impregnation into deciduous 

 bulbils, and acting the part of phytoids in the propagation 

 of the plant. More commonly, perhaps, the viviparous 

 condition is induced by the force of circumstances, as a 

 compensating provision under a state of matters liable to 

 interfere with the maturation of the essential parts of fruc- 

 tification the stamens and pistils. Thus certain grasses 

 which have regular flowers in genial habitats, are found to 

 present the viviparous inflorescence in alpine situations ; 

 and cases are even met with in which the same individual 

 plant forms at one time gemmae, and at another time ovules, 

 within its floral envelopes, according to variations in climate 

 or other external circumstances. If we may assume in such 

 cases that the viviparous condition is in compensation for 

 the inability of the plant to form perfect stamens, there 

 would arise a certain probability of the actual transforma- 

 tion of the rudimentary ovule into a gemma, capable of 

 vegetating into a new plant, apart from any fertilizing ac- 

 tion of the pollen. 



For farther arguments on the essential identity of ovules 

 and gemmae, reference may be made to works on Vegetable 

 Morphology, in which this view is almost universally adopt- 

 ed. So much at least appears to be shown by the occurrence 

 of viviparous flowers, that the same focus of vital action 

 may be capable of assuming the form of a gemma, to pro- 

 pagate the plant by its unaided plastic powers or of be- 



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