x 
~N 
( 
go FLOWERING PLANTS 
kinds — brown scaly bracts, and, secondly, scales bearing 

Fig. 51.—A SINGLE PLACENTAL SCALE 
WITH Two OVULES. 
In the right-hand one the integument 
is removed, 
i.) A nucellus. | 
(i1.) An embryo-sac or macrospore, 
a large cell near the centre of the 
nucellus. 
It will be seen that there is only 
one integument, and it is thought 
that the scale bearing the ovule 
answers to the second or external 
integument which is present in 
Angiosperms. When the pollen grain 
falls to the bottom of the scale, 
it is sucked up by the micropyle 
owing to the drying up of the 
mucilage in the micropyle, so that 
the pollen grain now rests on the 
nucellus ; then it puts out the pollen- 
tube, the growth of which is soon 
arrested. As soon as this has taken 
ovules. These ovuli- 
ferous scales, are dle- 
veloped on the upper 
surface of the bract 
scales, and bear on 
their upper  -surface 
two ovules or macro- 
sporangia. The illustra- 
tion shows ovules at 
different stages of de- 
velopment. 
A section of an ovule 
shows— 
(i.) One integument, 
with the micropyle, 
which is turned _to- 
wards the stem. 
A) 
HS 
re 
rt 
z 

Fig. 52.—-OVULE oF PINUS; 
Mep1An Secrion. (High 
powet. ) 
4, integument ; n, nucel- 
lus; e, embryo-sac ; m, ml- 
cropyle ; p, pollen-tube. 
place, the endosperm begins to be formed ; the cells of the 
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