246 ORR—THE OVvULAR INTEGUMENTS AND TESTA 
integument, at a relatively early stage in the development of the 
ovule, seems to imply a more definite purpose. | 
At a later stage the thick-walled tissue extends upwards in 
the inner integument, the large cells of the aqueous tissue be- 
coming thick-walled and fibrous in character, this change in 
configuration extending gradually backwards to the base of the 
integument, until ultimately a compact fibrous testa is formed 
which completely envelops the seed. The fibres composing the 
testa are long, narrow, pitted elements, differing markedly from 
those of Capparis, which are extremely irregular in shape. 
The original thick-walled tissue developed in the region of the 
micropyle has now become sclerotic in character, but, as is also 
the case with the fibres of the rest of the testa, the protoplasmic 
I 2 
FIG. 3. mye: from the outer integument of the ovule of Cleome spinosa, 
n (1) surface view, and (2) section. x about 50 
contents are still visible, and it is difficult to say definitely at 
what stage they disappear. 
In the seed the function of this fibrous envelope is obviously 
that of protecting the embryo and preventing desiccation ; 
but its genesis in the organic apex of the inner integument in 
the immature ovule, its interrupted development, and the 
retention of the living contents by the thick-walled cells round 
the micropyle all seem to predicate another function at the time 
ot its inception. 
In the mature ovule, as already indicated, the outer integu- 
ment is double-layered, except at the micropyle, and in the 
outermost layer stomata occur. These stomata are compara- 
tively numerous, and are identical with the similar organs in 
the leaf of Cleome. Where a stoma occurs, the two layers of 
the integument are separated, and an intercellular space is 
formed into which the stomatal pore opens, thus bringing the 
underlying tissue into direct communication with the ovarian 
cavity. 
