eP PHARMACEUTICAL BOTANY 
are pollinated by snails and slugs when they are called Mat- 
ACOPHILous. These have dark colored flowers. 
Before the pollen grain has been deposited upon the stigma 
and during its germination thereon, a series of events affecting 
both the pollen grain and the embryo sac occur which result in 
the ultimate formation of the male and female gametophytes. 
MATURATION AND FERTILIZATION 
(In ANGIOSPERMS) 
MATURATION OF THE POLLEN GRAIN AND FORMATION OF THE 
MA e GAMETOPHYTE.—The substance of the microspore (pollen 
grain) divides into two cells, the mother and tube cells of the future 
male gametophyte. The nucleus of the mother-cell divides to 
form two sperm nuclei. Within the tube cell is found a tube 
nucleus embedded in protoplasm. Upon germinating the parti- 
tion disappears and the thin endospore (¢ntine), carrying within it 
the protoplasm in which are embedded the tube nucleus and two 
sperm nuclei, penetrates through a deficiency of the exospore 
(extine). The contents of the pollen grain at this stage is called 
the male gametophyte. 
MATURATION OF THE EMBRYO SAC AND FORMATION OF THE 
FEMALE GAMETOPHYTE.— The nucleus of the megaspore or embryo 
sac undergoes division until eight daughter-nuclei are produced 
which are separated into the following groups: 
(a) Three of these nuclei occupy a position at the apex, the 
lower nucleus of the group being the egg or ovum, the other two 
nuclei being the synergids or assisting nuclei. 
(b) At the opposite end of the sac are three nuclei known as 
the antipodals which apparently have no special function. 
(c) The two remaining nuclei (polar nuclei) form a group 
lying near the center of the embryo sac which unite to form a 
single endosperm nucleus from which, after fertilization, the 
endosperm or nourishing material is derived. This stage of the 
embryo sac constitutes the female gametophyte. 
FERTILIZATION IN ANGIOSPERMS.—After the pollen grain 
reaches the stigma, the viscid moisture of the stigma excites the 
outgrowth of the male gametophyte which bursts through the 
