552 
APPENDIX. 
[B. 
entirely exposed, the outer membrane being even then open 
its whole length ; and that the outer membranes of the two 
collateral ovula, which are originally distinct, cohere in a 
more advanced stage by their corresponding surfaces, and 
together constitute the anomalous dissepiment of the cap- 
sule ; the inner membrane of the ovulum consequently form- 
ing the outer coat of the seed. 
The inner membrane of the ovulum, 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 impreg- 
nation, its perforated apex projects beyond the aperture of 
the testa, and in some plants puts on the appearance of an 
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 is formed by the proper membrane or 
cuticle of the Nucleus, from whose substance in the unim- 
pregnated ovulum it is never, I believe, separable, and at 
that period is very rarely visible. In the ripe seed it is 
distinguishable from the inner membrane only by its apex, 
which is never perforated, is generally acute and more 
deeply coloured, or even sphacelated. 
The membrane of the nucleus usually constitutes the 
innermost coat of the seed. But in a few plants an ad- 
ditional coat, apparently originating in the inner membrane 
of Grew, the vesicula colliquamenti or amnios of Malpighi 
also exists. 
In general the Amnios, after fecundation, gradually en- 
larges, till at length it displaces or absorbs the whole sub- 
stance of the nucleus, containing in the ripe seed both the 
embryo and albumen, where the latter continues to exist. 
