194 ALTERATION OF POSITION. 



tiling has been noticed in Urtica dioica by Clos, * Bull. 

 Soc. Bot. France,' vol. 9, p. 7. 



Baillon (' Etudes du groupe des Euphorbiac^es,* p. 

 205) mentions the following species of that order as 

 having been seen by him with monoecious inflorescence : 

 Schismatopera distichophylla, Mozinna peltata, Hermesia 

 castaneifoUa. Oliver mentions (' Hook. Icon, Plant.,' 

 t. 1044) that in Lcitneria floridana the upper scales of 

 the male catkin occasionally subtend an ovary. 



It would seem that external conditions have some 

 effect in determining the formation of one sex, as in 

 some species of Garex, while in the case of Salix repens, 

 Hampe^ says that when grown partially or for a time 

 under water, those twigs which are thrust up above 

 the surface bear female flowers, while those twigs that 

 blossom after the water is dried up, produce male 

 flowers only. 



Carriere^ says that a plant of Stauntonia lati/olia 

 which for some years produced stamens only, now 

 produces flowers of both sexes ; it was dioecious, but 

 is now monoecious. The same author alludes to a 

 similar occurrence in Juniperus Virginiana. The nut- 

 meg is also said to vary in sexual characteristics from 

 time to time." In addition to the genera, already 

 named, in which this production of flowers of both 

 sexes has been observed may be mentioned Tamis ! 

 Chmnera ! Urtica ! Mercurialis ! Bestio ! Cannabis ! 

 Salix ! Huinulus ! as well as others in which the 

 change is less frequent. 



Among cryptogams a similar change occurs. As an 

 illustration may be cited Leucobryum giganteum, as 

 quoted from Midler in Henfrey's 'Botanical Gazette,' i, 

 p. 100. 



As to androejnoas willows, in addition to the references given under 

 the head of Soostitution of stamens for pistils, see Schlechtendal, ' Flora 



' * Linna^a,' xiv, 367. 



' Rev, Hortic.,' January, 1867. 



See Royle, ' Man. Materia Medica,' ed. 1, p. 567. 



