42 
developed pollen tube. 
PISTILS AND STAMENS 
This feature is shown in Figure 49. The 
nucleus at the end of the tube and known as tube nucleus directs 
the growth of the tube and disappears 
soon after reaching the embryo sac. 
The two nuclei following closely be- 
hind the tube nucleus are the sperms 
or male nuclei, the structures which 
join with the egg and primary endo- 
sperm nucleus in fertilization. The 
pollen tube is a passage way through 
which the sperms pass to the embryo 
sac. 
Fertilization. After the two sperms 
reach the embryo sac, one approaches 
the egg and fuses with its nucleus, while 
‘ ‘ss Tage tte * = 
Fic. 49. — Pollen grains in different stages 
preparatory to fertilization. A, surface view 
of a pollen grain; B, section through pollen 
grain in uni-nucleate stage; C’, section through 
pollen grain showing the nucleus divided into 
the generative (g) and tube nucleus (); D, 
pollen tube forming into which the two nuclei 
have passed; HZ, tube more developed and 
generative nucleus divided into two sperms 
(g). Much enlarged. 
Fic. 50,— A diagram of a length- 
wise section through the pistil of Red 
Clover, showing pollen tubes trav- 
ersing the stigma and style. Two 
pollen tubes have reached the em- 
bryo sacs. p, pollen grains develop- 
ing tubes; st, stigma; p.t, pollen 
tubes; 0, ovules; e, egg; en, en- 
dosperm nucleus; s, sperms. Much 
enlarged. 
the other approaches the primary endosperm nucleus and fuses with 
it. This process of fusion is called fertilization. Since there are two 
