244 
ORGANOGRAPHY. 
BOOK I. 
The integuments of a seed are called the testa ; the rudi- 
ment of a future plant, the embryo (Plate VI. fig. 1. &c.) ; 
and a substance interposed between the embryo and the testa, 
the albumen (fig. 1. a, 5. a, &c.) 
The testa, called also lorica by Mirbel, perisperm and 
episperm by Richard, and spermodermis by De Candolle, ac- 
cording to some consists, like the pericarp, of three portions ; 
viz., 1. the external integument, tunica externa of Willdenow, 
testa of De Candolle; 2. the internal integument, tunica 
interna of Willdenow, endopleura of De Candolle, kilofere and 
tegmen of Mirbel ; and, 3., of an intervening substance an- 
swering to the sarcocarp, and called sarcodermis by De 
Candolle : this last is chiefly present in seeds with a suc- 
culent testa, and by many is considered a portion of the 
outer integument, which is the most accurate mode of under- 
standing it. 
According to Schleiden, the integuments of the seed ex- 
perience many changes during the period of ripening, so that 
their original number can rarely be recognised. They are 
sometimes all consolidated so as to form but one ; or they are 
broken up into many layers, having no relation to the original 
number of integuments. In Menyanthes, which has but one 
integument of the ovule, the seed appears to have two, because 
of the separation and lignification of the epidermis of that 
integument ; and in Canna there are five layers of tissue re- 
sembling integuments, although the ovule has not even one 
complete integument. 
The cellular tissue of the integuments of the seed is very 
often reticulated. In most Bignoniaceae, and many other 
plants, the epidermis is in this state, and in Casuarina there 
is a layer of spiral vessels below the epidermis, very thin and 
delicate, and extremely minute. In Swietenia febrifuga there 
is, below the epidermis, a thick layer of large spiral cells, 
which have liitle cohesion with each other, and which form a 
multitude of rather large fusiform sacs lying confusedly (?) ; 
this is the most complete case of spiral cells in seeds 
with which I am acquainted, and it is accompanied by the 
presence of a bundle of numerous slender spiral vessels in the 
raphe. 
