The Life of the Plant. - IQI 
The processes concerned in fertilisation and the forma- 
tion of the embryo in Gymnosperms (Coniferze and Cycadez) 
differ somewhat from that now described, but correspond in 
all essential points. The differences are as follows: in 
Gymnosperms the pollen-grain falls directly upon the micro- 
pyle of the ovule, the pollen-tube being developed, not as in 
Monocotyledons and Dicotyledons from the pollen-grain itself, 
but from one of its daughter-cells (Fig. 366). The embryo- 
sac, at least in Coniferee, is filled up soon after pollination with 
endosperm, which, however, has only a transitory existence. 
Fic. 366.-— Fertilisation of Cupressus ie 367.—Fertilisation of A dies excelsa : 
senipervirens (Coniferz): I. a pollen- # pollen-grains ; Zs pollen-tubes ; ¢ two 
grain with its two cells; a extine ; corpuscules in the embryo- sac é, (x 60. ) 
6 intine; II. pollen-grain in which 
the pollen-tuke c has been formed. (x 300). 
After some weeks, or often only after some months, it is 
again absorbed, a fresh development of endosperm taking 
its place. In this latter are formed a few cells of larger 
size than the rest, the secondary embryo-sacs or corpuscules 
(Fig. 367), the number of which differs in different genera. 
After some time each of them splits up by a partition- 
wall into two cells, a smaller upper one, the zeck-cell, 
and a larger lower one, the central cell. The first forms the 
