106 ILLUSTRATIONS OF 
numerous deep hexagonal areoles, separated by crenate undu- 
lating ridges, a character more or less conspicuous, and com- 
mon to the seeds of all the species of this genus that I have 
examined; the embryo enveloped in copious albumen is 
cylindrical, the radical which points to the base of the seed, 
not far from the hilum, is slightly curved at its union 
with the cotyledons, which are somewhat clavate and half its 
length.* 
I take this opportunity of indicating the suggestion, judg- 
ing from specimens existing in Sir Wm. Hooker’s Herbarium 
that the Nicotiana quadrivalvis, Pursh. and the N. multivalvis, 
Lindl. both from the western coast of America, may belong to 
the new genus established by Dr. Hooker, under the name of 
Dictyocalyz, upon a plant found by Mr. Darwin in the island 
of Gallapagos ; but they require examination. 
The 4th section of Nicotiana proposed by G. Don, Dict. 
4. 466, in order to comprise the above species, under the 
title of Polydiclia must therefore be suppressed; the other 
species contained in this section (with what reason I cannot 
ascertain, as its seed is unknown) is certainly a plant of very 
opposite character, and appears to me for the reasons given 
in p. 101 to belong rather to Nierembergia. The N. solani- 
folia of Dr. Walpers, placed by him in this division (Rep. Bot. 
‘4, 12) has since been referred to the section Rustice. 
PETUNIA. 
The limits of this genus, as I have before observed, are not 
very definite, so that some species by different able botanists 
have been confounded with Nicotiana, Nierembergia, and Sal-~ 
piglossis. To Nicotiana a near approach is manifest, the 
most striking distinction being seen in the valves of its cap- 
sules, which are entire, while in the former they are cleft half 
way, or sometimes nearly to the base, but in Petunia though 
* A figure of this plant with sectional details is represented in, 
Plate 22, 
