228 BOTANY. 
young pollen-sacs undergo division into four parts, which 
become rounded and covered with a double coat or wall. 
The outer coat is often much thickened, and may be rough- 
ened by ridges or prickles (Fig. 128). 
483. The pollen-cells germinate in moisture, by sending 
out a tube which is a prolongation of the inner coat. In 
some cases there are cells or nuclei in the cell or tube, evi- 
dently representing the first stage (prothallium) in its last 
stages of suppression. The protoplasm of the cell passes 
freely down the tube to its extremity. 
484, The ovule-bearing leaves of Angiosperms bear still 
less resemblance to ordinary leaves than do the stamens. 
In the simpler cases the young leaf becomes curved so that 
its edges touch and finally grow together, forming the 
ovary, which usually tapers above into a style or stalk sup- 
porting a glandular structure, the stigma (Fig. 127,”). The 
whole ovule-bearing organ, com- 
posed of ovary, style, and stigma, 
is usually known as the pistil. In 
many plants several pistils grow 
together, and thus form a com- 
nd pistil. 
Fie. 129.—Very young ovules. Pee B 
ne, ovule-body; sc,inner,and pr, 485. The ovules grow upon the 
outer, coats just beginning to 
grow; fn, ovule-stalk. Magnified j 1 
Shae inner (i.e., upper) surface of the 
leaf which forms the ovary, or at 
its base (Fig. 127), or more frequently upon its margins. 
At first it is a sintple rounded outgrowth of a few cells; as 
it grows older a circular ridge arises upon it, which often 
is soon followed by another (Fig. 129, A and B). These 
ridges grow out and upwards so rapidly that they overtake 
and enclose the ovule-body, leaving but a small opening or 
pore. 
