210 
admit the oxygenation of the air through them to an adapted set of aiteiies 
on their internal surface, according to the curious observations of Dr. Priest¬ 
ley on the oxygenation of the blood by the air through the moist membranes 
of the lungs. 
It should be here observed, that many seeds, before they fall on the 
moist earth, are included in a bag of air, as those of the staphylea, (bladder - 
nut) ; of the physalis alhekengi, (winter-cherry) 5 ofcolutea, (bladder-senna), 
in the pods of peas and beans; in the cells surrounding the seeds of apples 
and pears; and in the receptacle of ketmia, which probably serves to oxy¬ 
genate the blood of the infant seed, which in these plants may thus be of 
forwarder growth, before it is shed upon the soil. 
There exists a series of glands, and their ducts, improperly called umbi¬ 
lical vessels by some writers, which supplies the seed with nourishment 
from the parent plant, so long as it adheres to the ovarium of its mother, as 
the vessels by which a pea adheres to the pod, in which it is included; in 
fruits and nuts, where the kernel is covered with a stone or shell, a long 
cord of vessels passes into the bottom of the stone or shell, and rising to 
the top bends round the lobes of the kernel, and is inserted near or into the 
corculum or heart of the seed, where the living principle resides, and affords 
not only present nutrition to the vegetable embryo, but also secretes the 
farinaceous or oily materials for its future nourishment, which constitute the 
cotyledons of the seed. 
But the vessels, which may be properly called umbilical, pass from the 
heart or corculum of the seed, which is the living embryo of the future 
plant, into the seed-lobes, commonly called cotyledons, and imbibe from 
thence a solution of the farinaceous or oily matter there deposited foi the 
nutriment of the new vegetable. These vessels are delineated in their mag¬ 
nified appearance by Dr. Grew, and are by him termed seminal roots. 
These umbilical vessels probably consist of a system of absorbents, which 
supply nutriment to the embryo plant from the cotyledons of the seed, and 
also of a system of placental arteries and veins spread on the humid mem¬ 
brane, which covers the cotyledons, and is moistened by its contact with the 
earth, for the purpose of oxygenating the vegetable blood. This idea is 
countenanced by many plants bringing up their cotyledons, or seed-lobes, 
out of the ground into the air, which are then converted into leaves, and 
perform the office of lungs, after they have given up beneath the soil the 
nutriment which they previously contained, as in the young kidney-bean, 
