UNIREXUALITY. 105 



Berol.,' ii, p. 259. Tausch, ' Bot. Zeit.,' 1833, i, p. 229. Koch. ' Synope. 

 Flor. Germ.,' 740. Host, ' Flor. Aiist.,' ii, p. 641 (S. mirabUis). See 

 also Hegelmaier, ' Wiirttemberg Naturwissenscbaft Jahreshef te,' 1866, 

 p. 30. Other references to less accessible works are given in ' Linnasa,' 

 xiv, p. 372. 



Change from hermaphroditism to nnisexaality. Many 

 flowers ordinarily hermaphrodite as to structure, be- 

 come unisexual by the abortion or suppression of 

 their stamens, or of their carpels, as the case may be. 

 This phenomenon is lessened in interest since the 

 demonstration of the fact by Darwin and others, that 

 many plants, structurally hermaphrodite, require for the 

 full and perfect performance of their functions the co- 

 operation of the stamens and pistils, belonging to dif- 

 ferent individuals of the same species. 



Some of the Banunculacece constantly exhibit a ten- 

 dency towards the dioecious condition, and the rarity 

 with which perfect seeds of Ranunculus Ficaria are 

 formed is to be attributed, in great measure, to the 

 deficiency of pollen in the anthers of these flowers. 

 Ranunculus auricomus also is frequently sterile. Speci- 

 mens of Ranunculus bulbosus may be met with in which 

 every flower is furnished with carpels, most of which 

 have evidently been fertilised, although there are no 

 perfect stamens in the flowers. 



Knight and other vegetable physiologists have been 

 of opinion that a high temperature favours the pro- 

 duction of stamens, while a lower degree of heat is 

 considered more favorable to the production of pistils, 

 and in this way the occurrence of "bhnd" strawberries 

 has been accounted for. Mr. R. Thompson, writing 

 on this subject, speaks of a plantation of Hautbois 

 strawberries which in one season were wholly sterile, 

 and accounts for the circumstance as follows : 

 the plants were taken from the bearing beds the 

 year previous, and were planted in a rich well-manured 

 border, in which they started rapidly into too great 

 luxuriance, the growth being to leaves rather than to 

 fruit. The following season those same plants bore 



