194. ALTERATION OF POSITION. 
thing has been noticed in Urtica dioica by Clos, ‘ Bull. 
Soc. Bot. France,’ vol. 9, p. 7. 
Baillon (‘ Etudes du groupe des Euphorbiacées,’ p. 
205) mentions the following species of that order as 
haying been seen by him with moncecious inflorescence: 
Schismatopera distichophylla, Mozinna peltata, Hermesia 
castaneifolia. Oliver mentions (‘ Hook. Icon. Plant..,’ 
t. 1044) that in Leitneria 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 Carex, 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 latifolia 
which for some years produced stamens only, now 
produces flowers of both sexes; it was dicecious, but 
is now moncecious. 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 Tawus! 
Guinera! Urtica! Mercurialis! Restio! Cannabis ! 
Saliz! Humulus! as well as others in which the 
change is less frequent. 
Among cryptogams a similar change occurs. As an 
illustration may be cited Leucobrywn gigantewm, as 
quoted from Miillerin Henfrey’s ‘ Botanical Gazette,’ i, 
p- 100. 
As to androgynous willows, in addition to the references given under 
the head of Substitution of stamens for pistils, see Schlechtendal, ‘ Flora 

1 «Linnea,’ xiv, 367. 
? ‘Rev. Hortic.,’ January, 1867. 
5 See Royle, ‘Man. Materia Medica,’ ed. 1, p. 567. 
