251 
I cannot but think that the true use of the vitellus may be to perform 
the functions of a cotelydon with regard to air if not to light, till a real leaf 
can be sent forth, and that the “ subterraneous cotyledons” of Gsertner in 
the Horse Chesnut and Garden Nasturtium are, as he seems to indicate in 
his Introduction, p. 151, rather of the nature of a vitellus. It does not 
appear that any plant with genuine ascending cotyledons is likewise fur¬ 
nished with this organ; on the other hand, it commonly belongs to such as 
have the most copious albumen , and therefore should seem to answer some 
other end than mere nutriment, which is supplied by the latter. 
We learn, from the above inquiries, that the old distinction between 
plants with one cotyledon and those with several may still be relied on, 
in the former the part which has commonly been so denominated 
is the albumen , as in Corn, the real cotyledon of which is the scale or 
vitellus ; which last organ, however, seems wanting In Palms, Lilies, fee. 
such having really no cotyledon at all, nor any thing that can perform its 
office, except the stalk of their embryo/* In the Horse Chesnut , Oak, and 
Walnut , possibly, whose seed-lobes do not ascend, the functions of a real 
cotyledon, as far as air is concerned, and those of the albumen, may be 
united in these lobes, as is the case with most leguminous plants; which Is 
rendered more probable, as several of the latter have the corresponding parts 
likewise remaining under ground. Hence the divided vitellus of the Cyamus 
Is to be considered as a pair of subterraneous cotyledons, and the plant con¬ 
sequently ranges near its natural allies the Poppy tribe, as Mr. Salisbury, 
without the aid of physiology, has shown in the Annals of Botany, f v. 2, 
P-7 o, 75- 
* This may answer the purpose of a cotyledon, just as the stems of many plants fulfil the office 
of leaves. 
f As to the other parts, to use the language of Grertner, Testa, the skin, contains all the parts 
of a seed above described, giving them their due shape; for the skin is perfectly formed, while they 
are but a homogeneous liquid. This coat differs in thickness and texture in different plants. It is 
sometimes single, but more frequently lined with a finer and very delicate film, called by Gmrtner 
membrana, as may be seen in a Walnut, and the kernel of a Peach, Almond, or Plum. In the 
Jasmine a quantity of pulp is lodged between the membrana and the testa, constituting a pulpy 
seed, semen baccatum, wdiich is distinct from the acinus, or grain of a compound berry in the 
Raspberry, the seed of the latter having its proper double covering within the pulp. The testa, 
bursts irregularly, and only from the swelling of its contents in germination. 
Hilum, the scar, is the point by which the seed is attached to its seed-vessel or receptacle, and 
through which alone life and nourishment are conveyed for the perfecting its internal parts. Con¬ 
sequently all those parts must be intimately connected with the inner surface of this scar, and they 
are all found to meet there, and to divide or divaricate from that point, more or less immediately. 
