PLANT ORGANS AND ORGANISMS 1 69 
is occasionally present and is called the Aril. Example: Euonymus 
(succulent). 
When such an integument arises from the dilatation of the micro- 
pyle of the seed, as in the Nutmeg, it is known as an Arillode. 
The Nucellus or Kernel consists of tissue containing albumen, when 
this substance is present, and the embryo. Albumen is the name 
given the nutritive matter stored in the seed. The funiculus or seed 
stalk is usually absent in the official seeds. The scar left by its 
separation is called the hilum. When the funiculus is continued 
along the outer seed coat, it is called the raphe. 
MODE OF FORMATION OF DIFFERENT TYPES OF ALBUMEN 
If the egg-cell within the embryo sac segments and grows into the 
embryo and, stretching, fills up the cavity without food material 
laid down around it, it happens that the nutritive material lingers in 
the cells of the nucellus pressing around the embryo. This is called 
Peris per mic albumen. Seen in the Polygonaceoe. 
In by far the greater number of Angiosperms, the endosperm nu- 
cleus, after double fertilization, divides and redivides, giving rise to 
numerous nuclei imbedded in the protoplasm of the embryo sac, out- 
side of the developing embryo. Gathering protoplasm about them- 
selves and laying down cell walls they form the endosperm tissue 
outside of the embryo. Into this tissue food is passed constituting 
the Endospermic albumen. 
In the Marantaceoe, Piperacece, etc., nutritive material is passed 
into the nucellar cells causing them to swell up, while to one side a 
small patch of endosperm tissue accommodates a moderate amount 
of nourishing substance, thus resulting in the formation of abundant 
perisperm and a small reduced endosperm. 
Exalbuminous seeds are those in which the albumen is stored in the 
embryo during the growth of the seed. Such seeds show the fleshy 
embryo taking up all or nearly all the room within the seed coat. 
Examples: Physostigma, Amygdala, etc. 
Albuminous seeds are those in which the nourishment is not stored 
in the embryo until germination takes place. Such seeds show a 
larger nourishing tissue region and a smaller embryo region. Exam- 
ples: Nux Vomica, Myristica, Linum, etc. 
