208 
ORGANOGRAPHY. 
BOOK I. 
here called secundine is not primine, and the supposed pri- 
mine arillus. 
The inner membrane (secundine) of the ovule, however, 
in general appears to be of greater importance as connected 
with fecundation, than as affording protection to the nucleus 
at a more advanced period. For, in many cases before im- 
pregnation, its perforated apex projects beyond the aperture 
of the testa, and in some plants puts on the appearance of ah 
obtuse, or even dilated stigma; while in the ripe seed it is 
often either entirely obliterated, or exists only as a thin film, 
which might readily be mistaken for the epidermis of a third 
membrane, then frequently observable. 
" This third coat (tercine) is formed by the proper mem- 
brane or cuticle of the nucleus, from whose substance in the 
unimpregnated ovule it is never, I believe, separable, and at 
that period is very rarely visible. In the ripe seed it is dis- 
tinguishable from the inner membrane only by its apex, 
which is never perforated, is generally acute and more deeply 
coloured, or even sphacelated." 
Mirbel has, however, justly remarked that the primine and 
the secundine are, in the . seed, very frequently confounded; 
and that, therefore, the word testa is better employed, as one 
which expresses the outer integument of the seed without 
reference to its exact origin, which is practically of little im- 
portance. The tercine is also, no doubt, often absent. He 
observes that these mixed integuments often give rise to new 
kinds of tissue ; that in Phaseolus vulgaris the testa consists, 
indeed, of three distinct layers, but of those the innermost 
was the primine; and that the others, which represent nothing 
that pre-existed in the ovule, have a horny consistence, and 
are formed of cylindrical cellules, which elongate in the 
direction from the centre to the circumference. And this is 
probably the structure of the testa of many Leguminosae. 
It sometimes happens that the endopleura (or tercine?) 
thickens so much as to have the appearance of albumen, as 
in Cathartocarpus fistula. In such a case it is only to be dis- 
tinguished from albumen by gradual observation from the 
ovule to the ripe seed. 
