TRANSACTIONS OF THE SECTIONS. 87 



071 Datura Stramonium and Datura Tatula. 

 Bij Professor BucEMAif, F.L.S., F.G.8. 



The object of this paper was to show that Datura Stramonium and D. Tatula 

 were identical in points of strncturo, and therefore conld only be considered as 

 vai'ieties of a single species. That the heightened colour in the flowers, stems, 

 and leaf-nervures in the D. Tatula, when compared with 2>. Stramojiium, wiU be 

 a deeper purple in proportion to the warmth of the sununer, the milder climate, 

 and amount of sun to which it is exposed. That though identical in species, the 

 fine forms of the D. Tatula, as much as six feet high, are very distinct in medicinal 

 properties, as indicated by a more powerful smell, and evidenced by the almost 

 disuse of the D. Stramonium and the increasing emploj-ment of D. Tatula in 

 asthmatic and chest complaints. 



On, the Decay of Species, and on the Naturcd Provisions for Extending their 

 Duration. By Dr. Datjbent, F.E.S., F.L.S., Professor of Botany, Oxford. 

 It may be assumed as an acknowledged fact, not only that every organized being 

 has a limit assigned to its existence, but also that the species themselves, both in 

 the animal and vegetable kingdom, wear out after a certain period. But it stiU 

 remains to be inquu-ed whether there may not be certain natural contrivances for 

 postponing this inevitable termination to a later period than would otherwise 

 happen. Confining himself to the vegetable kingdom, the author suggested that 

 one of these provisions woidd seem to be the introduction of new varieties, which, 

 by diverging somewhat from the original t^'pe, acquire fresh vigonr, and thereby 

 tend to prolong the existence of the species from which they are derived. One of 

 the modes by which this variation in character is secured follows as a consequence 

 from the mode by which plants are reproduced through the instrumentality of the 

 'floral organs, by the concm-rent action of which an iudi\-idual, intermediate in 

 cliaracter between its respective parents, and therefore slightly diverging from 

 both, is the result ; so that this mode of multiplying the indiidduals of a species 

 seems to fulfil an important subsidiary end, even in cases where, as in plants of 

 low organization, the increase of the species is sufficiently provided for by means 

 of buds. Accordingly plants propagated by cuttings seem in general to adhere 

 more vmiformly to the same type, and at the same time to be more limited in their 

 duration than those produced from seeds. But this de^N-iation from the primaeval 

 t^'pe is still more completely earned out when the poUen of one plant is made to 

 act upon the embryo of another; and hence may arise those numerous contri- 

 vances for preventing self-fertilization which Mr. Darwin and others have pointed 

 out. To the same cause, perhaps, may be owing the increased vigoiu" which a 

 plant acquires by being removed into a fresh soil, or into a distant coimtry. 

 !\Iauy, no doubt, will regard it as a sufficient explanation of these facts, to appeal 

 to the changes produced in the constitution of a plant by such causes, as tending 

 to multiply the chances of some members of the species becoming adapted to those 

 alterations in the external conditions which occm* in the course of time, and which 

 might otherwise have proved fatal to its continued existence. There are, however, 

 reasons for believing that this solution will not embrace aU the facts of the case, 

 and that, even when every facility for producing the utmost amount of variation of 

 which a species is susceptible exists, a period at length anives when a species dies 

 out, although the climate, soil, and other external conditions continue, so far as 

 we can perceive, propitious. 



On the Old Welsh Mistletoe Cure for St. Vitus' s Dame. By M. Moggeidge. 



On Euphorbiacete. By Dr. Mullee. 



On Balatta and other Gums regarded as a Substitute for Gutta Percha. 



By Dr. E. Eiddell. 

 The author spoke of the gum as a very excellent substitute for, and quite equal 

 to, the adulterated or reboiled gutta percha from Singapore. They were indebted 



