80 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
other fuses with the central or " polar " nucleus, and lays the foundation 
of the endosperm. 
The impregnated germ-cell now enters upon a new life. Though 
called a " cell " it is really a nucleus with protoplasm, hut without any 
cell-wall at all. This is now secreted, and a complete cell is thus made, 
in the usual sense of the term. It divides into two, and then again and 
again, but in one direction, making a row of cells called the " suspensor." 
It is not till after some time that the terminal cell divides at right angles 
to the other previous divisions. These two cells are the commencement 
of the embryo : they rapidly increase in number till a globular mass called 
the " pro-embryo " is formed. 
In some plants, as Orchids, certain parasites and saprophytes, the 
embryo never progresses beyond this stage before germination. 
While the embryo is thus in preparation, the central nucleus, now 
impregnated, divides into many nuclei, at first free in the general proto- 
plasm of the embryo-sac. Gradually cell-walls are formed between them ; 
so that the endosperm finally consists of a mass of cells filled with starch 
&c. for future use. 
In many cases as fast as endospermal tissue is formed it is dissolved 
and consumed by means of the suspensor, the nourishment being conveyed 
into the embryo for its growth. This proceeds until all the endospermal 
tissue is gone ; when the embryo becomes relatively large, having the 
tissue of its own cotyledons full of starch, oil, and aleurone &c. instead. 
We will now follow the development of the pro-embryo : it is soon 
seen to change its form from a globular mass of cells to a heart-shaped 
body by a depression at the terminal point, in consequence of its growing 
more rapidly at two points. These two lobes are the foreshadowings of 
the two cotyledons, if it be a dicotyledonous plant. 
If it be a monocotyledon, then one point only grows, and taking up 
a median line a slight depression appears at one side. There is much 
reason for believing that this arises from an arrest of one cotyledon. 
Indeed, both Asparagus and Buscus have a rudiment of a second 
cotyledon, although they belong to the class Monocotyledons. 
When the ovule has become a ripened seed, we. find the coats have 
developed into the seed-skin ; or various changes may take place, as in the 
absorption of the inner one ; the outer part of the central body may form 
part of the skin as well. 
A seed of an Orchid will illustrate the final result when the embryo 
was arrested at its early stage of pro-embryo. A grain of Wheat is one 
in which the endospermal tissue was abundantly formed, and a Pea, Bean, 
or Almond are cases in which the endosperm was all consumed before the 
embryo grew to maturity. 
