182 CONTRIBUTIONS TO 



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 guadrivalvis, 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 

 Dictyocalyx, 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, Diet. 

 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. 177 to belong rather to Nierembergia. The N. solant- 

 folia of Dr. Walpers, placed by him in this division {Rep- Bot. 

 4. 12) has since been referred to the section Rustica. 



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 bo ~ 

 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 h a 

 way, or sometimes nearly to the base, but in Petunia thoug 



• A figure of this plant with sectional details is represented in Pl ate 

 of the " Illustrations of South American Plants." 



