190 BRITISH PLANTS 
sorrel. Thejhorse-chestnut forms a curious kind of cap- 
sule. Its ovary is composed of three carpels, and is three- 
chambered, with two seeds in each chamber. But one 
seed in one chamber alone develops; the others abort. 
Two of the chambers are crushed out by the pressure of 
the successful seed, and the result is a one-seeded fruit. 
Occasionally two seeds share the food 
between them, and we get a two-seeded 
“nut.” When ripe, the outer shell, 
which is thick and succulent, splits apart 
into three pieces, and the seed is released. 
3. Sehizocarps (Gr. schizo, I split), or 
separati@ig-fruits, are derived from syn- 
carpous ovaries formed from two or more 
carpels. There are usually as many 
chambers as there are carpels, with one 
seed in each. When the fruit is ripe, 
the carpels separate from each other into 
a number of one - seeded indehiscent 
sections (mericarps: Gr. meros, a part). 
Each of these is biologically an achene. 
In the maple and sycamore (Fig. 94) 
the fruit consists of two or three winged 
carpels, which ultimately separate into 
one-seeded portions. It is a double 
samara, or key. The fruit generally 
leaves the tree whole, forming a kind of 
shuttlecock, which spins round in the 
wind and describes a zigzag course in its 
descent. 
ae In the geranium five carpels split 
sHowine THE away from each other and from a column 
EROU ates which is an upgrowth of the receptacle. 
yrom Centra, Ln the cultivated geraniums (Pelargon- 
PartIvION. zum), the style forms a curved awn set 
with a fan of silken hairs. In the wild 
geraniums, or crane’s-bills (Geranium), the hairs are absent, 
and the mericarps break away from the column with 
such force that in some species (G. Robertianum, G. 
lucidum, G. pheum, G. molle, and G. pusillum) the seeds 
are actually shot out of their carpels ; the mericarps are 
then known as cocci. In the stork’s- bill (Hrodium, 
Fig. 95) a spirally-twisted awn is provided with a fan of 
