362 
PLANT STUDIES 
FIG. 323. Cross - section of 
anther of a li]y (Butomus), 
showing the separating walls 
between the members of each 
pair of sporangia broken 
down at z, forming a con- 
tinuous cavity (pollen-sac) 
which opens by a longitudi- 
nal slit. After SACHS. 
The opening of the pollen-sac to discharge its pollen- 
grains (microspores) is called deMscence, which means " a 
splitting open," and the methods of 
dehiscence are various (Fig. 322). 
By far the most common method 
is for the wall of each sac to split 
lengthwise (Fig. 323), which is 
called longitudinal deliiscence ; an- 
other is for each sac to open by a 
terminal pore (Fig. 322), in which 
case it may be prolonged above into 
a tube. 
241. Megasporophylls. These 
are the so-called " carpels " of Seed- 
plants, and in Angiosperms they 
are organized in various ways, but 
always so as to inclose the mega- 
sporangia (ovules). In the simplest 
cases each carpel is independent (Fig. 324, J), and is dif- 
ferentiated into three regions : (1) a hollow bulbous base, 
which contains the 
ovules and is the 
real seed case, 
known as the 
ovary; (2) sur- 
mounting this is a 
slender more or less 
elongated process, 
the style; and (3) 
usually at or near 
the apex of the style 
a special receptive 
surface for the pol- 
len, the stigma. 
In other cases 
several carpels to- 
B 
FIG. 324. Types of pistils : A, three simple pistils 
(apocarpous), each showing ovary and style tipped 
with stigma ; B, a compound pistil (syncarpous), 
showing ovary (/), separate styles (g), and stigmas 
^ ' ^ a cora P und P istil (syncarpous), showing 
ovary (f), single style (g), and stigma (n). After 
BERG and SCHMIDT. 
