196 ALTERATION OF POSITION. 
a most abundant crop, hence these plants were acci- 
dentally prevented from perfecting their female organs.’ 
Mr. Darwin’ cites from various sources the following 
details relating to strawberries which it may be useful 
to insert in this place, as throwing some heht upon 
the production of unisexual flowers. ‘‘ Several English 
varieties, which in this country are free from any such 
tendency, when cultivated in rich soils under the 
climate of North America commonly produce plents 
with separate sexes. ‘Thus, a whole acre of Keen’s 
seedlings in the United States has been observed to be 
almost sterile in the absence of male flowers; but the 
more general rule is, that the male plants over-run the 
females. . . . The most successful cultivators 
in Ohio plant, for every seven rows of pistillate flowers, 
one row of hermaphrodites, which afford pollen for 
both kinds; but the hermaphrodites, owing to their 
expenditure in the production of pollen, bear less fruit 
than the female plants.” 
Stratiotes aloides has been said to produce its carpels 
with greater abundance towards the northern lmits 
of its geographical distribution, and its stamens, on 
the other hand, are stated to be more frequently de- 
veloped in more southern districts. 
Honckenya peploides affords another illustration of the 
sexual arrangements in the flower being altered as it 
would seem by climatal conditions. Thus, in the 
United States, according to Professor Asa Gray, the 
flowers are frequently hermaphrodite, while in this 
country they are usually sub-dicecious.® 
Treviranus* says that the flowers of Hippuris and 
Callitriche are apt to be hermaphrodite in summer, but 
female only at a later period. 
For further remarks on this subject, see sections 
relating to suppression of stamens and pistils. 
1 Thomson, ‘Gardener’s Assistant,’ p. 577. 
2 * Variation of Animals and Plants,’ i, 353. 
> Babington, ‘ Ann. Nat. Hist.,’ vol. ix, 1852, p. 156. 
“ «Phys. der Gewiichse,’ i, p. 325. 
