THE BOTANY OF SOUTH AMERICA. 149 



Before concluding these remarks, I will offer some further 

 observations upon the genera constituting the suborder Rec- 

 tembryete, among which I have noticed a feature hitherto 

 unobserved, and although not universal among all the genera, it 

 offers in most cases a very decided character; I allude to 

 the position of the ovarium upon a well-marked and distinct 

 columnar support. In Petunia and Nicotiana the ovarium 

 is sessile upon an annular disc, which surrounds and conceals 

 this support: in Petunia this disc is 2-lobed, in Nicotiana 

 it is generally 4-lobed. In Metternichia it is sessile,* without 

 any glandular appendage. Among those possessing a stipitate 

 ovarium, Fabiana has 2 oblong erect free glands, fixed on 

 the column, while in Vesiia an annular ring invests the 

 stipes and supports the ovarium. In Nierembergia, Sessea, and 

 Cestrum, (including Habrothamnus), the column is simple, 

 quite free, and generally without any glandular appendage, 

 or at least one that is not always easily perceptible. In 

 Sessea, Cestrum, Vestia, Nier ember gia, and Petunia, the tube 

 of the corolla is circumscissile, leaving a persistent cupuli- 

 form base that, in some cases, nearly incloses the ovarium, 

 a character I have before pointed out, as existing in some of 

 the Nolanacece. 



I have observed also in the Rectembryea, that the surface 

 of the testa in the seeds affords a variable character: in 

 Metternichia and Sessea, it is chartaceous ; in Cestrum, mi- 

 nutely reticulated and favose ; in Vestia, broadly rugose, 

 with fine transverse striae; in Nierembergia, with polished 

 prominent rugce ; and in Fabiana, it is nearly smooth, with 

 almost imperceptible, longitudinal, rugose striae. In Petunia 

 it is divided into large, equal, hexagonal hollows, separated 

 by simple ridges, while in Nicotiana these ridges are waving, 

 crenulate, or even sometimes cristate when viewed by a 

 powerful lens. 



The pollen grains of Metterniclda and Sessea are spherical, 

 with 3 rounded mammiform equidistant points, and 3 inter- 

 mediate convergent lines; those of Cestrum, Fabiana and 



* This, however, is only apparently so, as the column is of the same 

 ttockness as the ovarium. 



