1897.] Mr Blackmail, The 'phenomena of Carbon Dioxide etc. 273 



(2) The phenomena of Carbon Dioxide production associated 

 with reduced vitality in plants. By Mr F. F. Blackman. 



By the aid of an apparatus (which was exhibited), specially 

 adapted for physiological research on very small outputs of carbon 

 dioxide, several new phenomena of this nature have been brought 

 to light in plants. 



These comprise the liberation of carbon dioxide produced in 

 the following four cases. Firstly, that resulting from the action 

 of temperatures between 40° C. and 50° C. on dry resting seeds : 

 at temperatures below 40° C. no appreciable formation of carbon 

 dioxide takes place, and at continued higher temperatures the 

 amount, which is at first large, does not remain so but steadily 

 falls off, indicating the decomposition of a definite limited quantity 

 of some substance. Secondly, the large amount of carbon dioxide 

 produced in the first few hours after wetting coarsely ground dry 

 seeds. This cannot be attributed to the action of micro-organisms 

 and is hindered by the action of chloroform and other poisons. 

 Thirdly, the varying production of carbon dioxide by the action 

 of volatile poisons and of fatal temperatures on living leaves. 

 Finally, the post-mortem production of carbon dioxide brought 

 about by subjecting recently killed leaves to the action of a 

 temperature of 100° C. This amount was shewn to vary with 

 the method of killing adopted, and evidence was forthcoming to 

 shew that in this, as in the other cases, these substances which 

 easily oxidise with liberation of carbon dioxide are in some way to 

 be associated with normal respiratory processes. 



(3) On the leaves of Bennettites. By A. C. Seward, M.A., 

 St John's College. 



In the second volume of the British Museum Catalogue of 

 Wealden plants 1 , I brought forward evidence in favour of including 

 Williamsonia gigas Carr., Williamsonia Carruthersi Sew., and 

 other species in the same family or even genus with the Lower 

 Cretaceous Bennettites. Although we have not as yet discovered 

 any example of Williamsonia gigas showing internal structure, 

 there are many reasons for believing that this Lower Oolite fossil 

 represents an inflorescence very closely allied to that of Bennettites 

 Gibsonianus Carr. The immediate purpose of this article is, 

 however, to bring forward evidence in support of the somewhat 

 discarded view that Williamsonia gigas is the inflorescence of the 

 plant which bore the pinnate fronds known as Zamites gigas L. 

 and H. It is by the gradual accumulation of facts and the cor- 

 relation of various observations, that we are occasionally able to 



1 "Catalogue of the Mesozoic plants in the Department of Geology" (Brit. Mus.) 

 The Wealden Flora, Part ii. 1895, p. 134. 



