174 Mr. J. Miers on several genera hitherto placed in Solanacese. 



7. Hyoscyamece. — This forms a very natural tribe, remarkable 

 for the very singular epigynous gland, hitherto I believe new in 

 the history of vegetable physiology, the origin and nature of 

 which it is desirable to ascertain. It cannot bear any analogy 

 with the true disc, which is always hypogynous in the superior 

 ovarium and epigynous in the inferior germen, and which is ge- 

 nerally admitted by botanists to be little more than a confluent 

 whorl of abortive stamens. In Cacabus it assumes the form of 

 an enlargement of the base of the style, but that it exists here as 

 a distinct organ is proved by the swelling seen within the matured 

 fruit, in the summit of the cavity of the cells. In Thinogeton it is 

 considerably larger, where it appears as a coriaceous thickening 

 of the chartaceous covering that forms the upper portion of its 

 dry berry. It is however most distinctly developed in Hyoscya- 

 muSf even in the young ovarium, in the form of a fleshy external 

 gland, which covers more than the superior moiety of the entire 

 germen, and on making a longitudinal section it is seen di- 

 stinctly adnate upon the true endocarpium : it forms therefore a 

 very good discriminating character of this tribe. The cause of the 

 opercular dehiscence of the fruit in Hyoscyamus is thus readily 

 accounted for, because while the lower half of the pericarpial 

 covering remains thin and membranaceous, the opercular portion 

 becomes hard and coriaceous, from the indurescence of the glan- 

 dular covering above-mentioned *. I have placed doubtfully in 



* Although in the above case it is easy to trace the cause of the opercular 

 dehiscence of the fruit, the same is not so readily accounted for in other cases ; 

 in Aiiagallis for example. In this last-mentioned instance, a distinct zonal 

 line may be seen in the thin pericarpial covering before the ripening of the 

 fruit, and it is along this that the membranaceous capsule afterwards bursts, 

 by a clean circumscissure. This zonal line however bears no relation to the 

 longitudinal true nervures, which may be distinctly traced in the pericarpial 

 covering, and which, extending from the style to the base, may be referred 

 to the midribs and marginal junctions of the original carpellary leaves : but 

 what is the nature of the line which traverses these nervures at right angles 

 across all the carpellary leaves? This is difficult to be accounted for, unless 

 we imagine it to arise from a cause somewhat analogous to the case of Hyo- 

 scyamus, only that instead of the line being the marginal limit of an epigy- 

 nous gland, it may be the edge of an original elementary hypogynous disc, 

 which by its subsequent growth and attenuation becomes hardly distin- 

 guishable from the rest of the pericarpium. On examining this pericarpial 

 covering, about the period of the fall of the corolla, this zonal line is seen 

 more transparent than the rest of its substance, and not opake, as is ob- 

 servable in the regular longitudinal nervures which may then be readily 

 traced ; at this period however, and even in the younger state of the ova- 

 rium, before this zonal line becomes distinguishable, the lower half of the 

 pericarpial membrane is decidedly of a more greenish hue than the upper 

 moiety. This appears to me the only theory on which we can account for 

 the dehiscence of the capsule in Anagallis, but in suggesting it, I confess 

 that I could not discern the fact of the original existence and ultimate at- 

 tenuation of such a disc as I have imagined. Although, generally speaking, 



