Campbell—The Embryo-sac of Pandanus. 785 
The development of the endosperm begins at the apex of the embryo- 
sac, and the first division walls are formed while the embryo is still very 
small (Text-fig. 2, A, b). The development of the endosperm tissue does 
not seem to differ in any way from the ordinary method, and no particular 
study was made of this point. Between the nuclei there arise simul¬ 
taneously the division walls, which form an irregular tissue increasing by 
division and growth until the whole embryo-sac is filled with a continuous 
mass of endosperm cells. 
The hard testa of the seed is derived mainly from the outer integu¬ 
ment, the inner integument being almost obliterated during the ripening 
of the seed. 
Text-fig. 2. a. Upper part of the ovule and embryo-sac of Pandanus coronatus , Martelli, 
showing a young embryo embedded in the endosperm, en. The shaded portion represents the 
tissue of the nucellus. x about 40. b. The embryo shown in A, more highly magnified. The 
round cell at the base of the four-celled embryo may be the suspensor, but this is not certain, 
c. An older embryo, embedded in the endosperm, en. x 225. D. A still older embryo, x 225. 
The arrow points towards the micropyle. 
Summary. 
1. The primary sporogenous cell is separated from the epidermis of 
the nucellus by several layers of parietal cells presumably derived from the 
division of a single primary tapetal cell. The cells of the nucellus adjacent 
to the embryo-sac sometimes show an appearance suggesting that they 
may be abortive sporogenous cells. 
2. The sporogenous cell divides into a large lower cell and a smaller 
