xxxiv PREFACE. 
forate. On this point, Dr. Lindley has the following 
remarks.. This third coat is formed by the proper 
membrane or cuticle of the nucleus from whose sub- 
stance in the unimpregnated ovulum, it is never, I be- 
lieve separable, &c. &c. 
There is no positive mark by which the embryonary 
sae may be characterised as it is likewise imperforate. 
But its immediate contiguity to the embryo will in all 
exalbumenous seeds at once decide its nature: traces 
of its original attachment are likewise often visible at 
one of its extremities. The component cells in com- 
posita have a grumous nucleus. 
I may here observe, that the seeds of this extensive 
family are not, at least in a great number of instances, 
akenia. In almost all I have exmained. The outer te- 
gument adheres to the cavity of the pericarpium, and 
in all separates with it. It is the embryonary sac 
that invests the embryo and separates with it. In albu- 
minous seeds, as I have mentioned the existence of 
the embryonary sac is difficult to trace, this is owing 
to its having become incorporate as it were with the 
albumen. ín others again its existence in the ripe 
-seed is very distinct, enveloping the albumen in the 
shape of a hyaline membrane. 
Various additions may take place on either surface 
of the outer intezument, hence the number of coats 
is frequently apparently increased. M. Mirbel was the 
first to point this out. 
With regard to the vascular supplies of the seed, 
I may remark that a sufficient number of observa- 
tions, have not been made on the exact period of — 
