THE SELF-FERTILISATION OF PLANTS. 
7 
permit, but often without or scarcely opening their flowers in 
the winter months. 
Malvaceae. — Large-flowered species of this order are strongly 
proterandrous. Thus Malva sylvestris will have shed all its 
pollen before the stigmas are elevated ; but M. rotundifolia , as 
Muller has shown, is self-fertile, by the stigmas maturing simul- 
taneously with the anthers, and bending down to intertwine them 
selves amongst the latter (fig. 22). The curvature of the stigma 
to secure self-fertilisation is generally due to the more rapid 
growth of the pistil under confinement of the petals, so that the 
styles are forced back. This position is then retained on the 
expansion of the flower. 
Linace^e. — Though the genus Linum has species usually 
dimorphic and physiologically self-sterile, it must be understood 
that these conditions are not absolute and unchangeable. There 
is no reason for supposing they cannot be lost in any case, as 
indeed they often are in some. Thus the Clove Pink is strongly 
proterandrous, yet became self-fertilising in three generations 
with Mr. Darwin. Linum perenne was physiologically self- 
sterile with Mr. Darwin, yet Mr. Meehan has found an instance 
of its being quite self-fertile in America. Linum catharticum 
on the other hand is not dimorphic at all, and can be crossed 
or self-fertilised (fig. 23). 
Gteraniace^i. — Our wild species of Geranium furnish inter- 
esting transitional conditions from the proterandrous state to 
the self-fertilising, the former being seen in large-flowering 
forms, as G. pratense ; the latter in the smaller ones, as G. pu- 
sillum. * The common garden Pelargoniums are usually pro- 
terandrous, often strongly so, as the “ oak-leaved ” or 66 lemon- 
scented ; ” but pale-flowered “ scarlet-geraniums ” (P. zonale) 
are perfectly self-fertilised by the stigmas being scarcely 
elevated above the anthers, and recurving amongst them 
(fig. 24). 
Oxalis and Impatiens have cleistogamous flowers. Figs. 
25-28 represent the former, and figs. 29-31 the latter, f 
Leguminos^e. — The papilionaceous corolla is obviously adapted 
to intercrossing, and in some cases the flowers are morpho- 
logically self-sterile ; but there are many small-flowered species 
which are self-fertilising (fig. 32). 
Rosacea. — The remarks made about Ranunculus , which has 
many stamens like the Rosacese, apply to this latter order. 
Several small-flowered species, as Potentilla Fragrariastrum , 
retain the incurved position of the stamens ; others, like Agri- 
* For details, see Lubbock’s “ British Wild Flowers in relation to 
Insects,” p. 43. 
t For descriptions, see below, p. 13. 
