98 
PLANT MORPHOLOGY. 
ing a part of the seed- coat, as in mustard. In other 
cases the two coats are so closely united that they are 
not easily distinguished, as in stramonium. 
The terms used in describing the kinds of ovules, 
as orthotropous, anatropous, campylotropous, etc., are 
retained in the description of the seeds; and in describ- 
ing the different parts of the seed some of the terms 
which were applied to the ovule are also retained, as 
chalaza and raphe ; the seed when ripe usually becomes 
detached from its stalk and the scar remaing is called 
the hiliim ; that part of the seed corresponding to the 
foramen of the ovule is more or less closed and is 
known as the micropyle ; the embryo develops in such 
a way that the tip of the root always points in the 
direction of the micropyle. 
Externally, the seed-coats vary considerably; they 
may be nearly smooth, as in ricinus ; finely pitted, as 
in the mustards ; prominently reticulate, as in staphi- 
sagria; hairy, as in cotton, or winged, as in the seeds 
of the catalpa. There are also a number of other 
appendages, these having received special names : the 
wart-like development at the micropyle or hilum of 
some seeds, as in castor-bean and violet, is known as a 
caruncle; in the case of sanguinaria, a wing-like devel- 
opment extends along the raphe, and this is known as 
the strophiole ; in some cases the appendage may com- 
pletely envelop the seed, when it is termed an arillus ; 
when such an envelope arises at or near the micropyle 
of the seed, as the mace in nutmeg, it is known as a 
“ false arillus,” or arillode. 
INNER MORPHOLOGY OF THE SEED. 
The seed -coat usually consists of from two to six 
layers of cells : (1) an outer layer or so-called epi- 
dermis, (2) a layer of sclerenchymatous cells or stone 
