24 BOTANY 
The castor-oil seed (Figs. 13-15) differs considerably 
from both bean and sunflower. At the pointed end is 
a spongy mass the caruncle, which rapidly absorbs 
water. If the seed be placed in hot water a bubble of 
air will come out of the micropyle, indicating that it 
is in the region of the caruncle. The advantage of 
this is obvious. On removing the skin it would appear 
as if there were not two cotyledons as in the bean and 
sunflower. As a matter of fact, in the castor oil bean 
the cotyledons are two flat bodies lying inside the oily 
mass that forms the bulk of the seed. This oily mass 
is called endosperm, and, like the cotyledons, serves 
to support the young plant. Seeds with endosperm 
are called albuminous while those without are termed 
exalbuminous. 
In most dicotyledons, i.e, plants that have two 
seed-leaves, the seeds are exalbuminous, while in all 
monocotyledons, 1.e., plants that have only one seed- 
leaf, they are albuminous. Now, with a sharp knife 
slice the castor seed longitudinally through its flatter 
sides into two fairly equal parts. As shown in Fig. 14, 
the cut edges of the two flat cotyledons will be seen 
with the radicle extending downwards from the point 
of junction below, and the tiny plumule pointing 
upwards just above it. Now slice another seed through 
its rounded sides as shown in Fig. 15. The desired 
result may not be attained till after several attempts, 
but finally, even without a lens, it should be possible 
to see the veining of the exposed surface of the cotyle- 
don. The radicle appears below, and, with great care 
and patience, it will be possible so to split a seed as to 
see the plumule as well. 
The reserve food in the endosperm consists of oil 
and protein, and does not respond to the test for starch. 
The cotyledons show abundant protein as well as oil. 
It may be mentioned in passing that the scarlet 
outgrowth forming the cup of the titoki seed is similar 
