Primitive Angiosperms . 153 
More time has been spent on the structure of Monocotyledons in which 
the early leaves appear terminal than such exceptional forms would deserve, 
were it not for the light which their structure throws on the normal forma- 
tion of an apparently terminal cotyledon. If there is reason to think that 
the influence of environment can effect a change in the configuration of the 
embryo and seedling so complete that the early leaves appear terminal 
owing to suppression of the stem, equally stringent conditions may account 
for the formation of an apparently terminal cotyledon. 
What are the conditions under which the embryo is formed within the 
embryo-sac? In general it may be considered as a mass of meristem 
developing in a confined space, feeding parasitically on the tissues of the 
mother-plant, and obliged to prepare for a period of rest followed by one of 
rapid growth and severe competition. 
The more obvious conditions which will affect the form of the embryo 
while it is developing within the embryo-sac are : 
1. The space at its disposal, depending partly on the shape of the 
embryo-sac, and partly on the development and texture of the endosperm. 
2. The method of food-supply. 
3. The configuration of the mature embryo — that is, of the embryo 
immediately before its exit from the seed. This again depends on two sets 
of conditions : the future form of the seedling, which is largely determined 
by its environment after germination, and the method by which the embryo 
will free itself from the tissues of the seed. 
We have very little exact knowledge on any of these points ; the 
following remarks on each are merely suggestive. 
1. The embryo-sac in the ripe seed of many species — Monocotyledons 
and Dicotyledons alike— is very often long, narrow, and sharply bent on 
itself. Mrs. Schaffner’s drawing of Capsella ( 76 , Fig. 37), Miss Gibbs’ 
drawing of Stellaria ( 28 , Fig. 22), and Professor Schafiher’s drawing of 
Sagittaria ( 75 , Fig. 73), show how the embryo has to accommodate itself 
in each case to its quarters. The embryo-sac continues to increase in size 
during the growth of the embryo, which in such forms is confined from the 
first within a long narrow space. It is further hampered by the presence of 
a growing endosperm. 
2. The food-supply of the pro-embryo is no doubt commonly conveyed 
through the suspensor. In some forms — as in many of the Leguminous 
species described by Guignard ( 31 ), and those from the Rubiaceae described 
by Lloyd ( 54 ) — the suspensor is very highly specialized as a haustorial 
organ, is massive and persistent. But, as a rule, it flourishes for a limited 
period only ; long before the seed is ripe the suspensor is withered and 
clearly no longer functional. Food must then reach the embryo in some 
other way. 
The cotyledons are generally understood to take over the absorptive 
M 
