80 WEDDEL, ON THE CYSTOLITES 



as in the cambium and in rhe telienchyma, where no part of 

 the wall at any age is coloured by sulphuric acid, owing to 

 the circumstance that the entire cell-wall in these situations is 

 composed of the cambial substance. It may thence be justly 

 concluded that an original chemical difference exists between 

 the deposit-layers of the cambial wall and the additional layers 

 of the second and subsequent generations ; and that this dif- 

 ference is manifested at a later period in the resistance offered 

 by this parietal layer to the expansive influence of acids and 

 alkalies. 



The period is but very brief, during which the additional 

 layers of the second and subsequent generations are reddened 

 by sulphuric acid. In a shoot of Pinus austriaca examined 

 on the 7th June, in which the annual ring had begun to be 

 formed in the early part of May, only the 16-18 outermost 

 fibres of each ray were reddened, whilst the older, 18-20 fibres 

 assumed a brown colour. This gives a period of 2 or 3 weeks 

 as the time during which the reddening effect of sulphuric 

 acid is manifested. 



On the Cystolites or Calcareous Concretions in the Urti- 

 CACEiE and other Plants. By H. A. Weddel, Aide- 

 Naturaliste in the Jardin des Plants. (From the Annales 

 d. Sc. Natur. Ser. IV., torn, ii., p. 267.) 



About the year 1827, J. Meyen discovered in the leaves of 

 Ficns elastica, and of several other species belonging to the 

 same genus, certain pedunculate corpuscles, constituted, as 

 he supposed, of gum or of some analogous substance ; he 

 ascertained that these corpuscles increased by the super- 

 position of new layers, and that ultimately they became covered 

 with notches and elevations composed of a calcareous, crystal- 

 line material, soluble with effervescence in acids (carbonate of 

 lime). 



Long after this discovery by Meyen, M. Payen undertook 

 the study of the same bodies, whose existence he demonstrated 

 in a great many other plants belonging to the family of the 

 Urticacece, and he concluded from his researches that their 

 constituent matei'ial, which was regarded by Meyen as being 

 of a gummy nature, was in fact cellulose, and that it was dis- 

 posed, not in concentric groups, but in true cells united into 

 racemose masses, each of which was destined for the secretion 

 of a certain quantity of carbonate of lime. This view, which 

 was adopted by several botanists, has been combated by others. 

 Thus Schleiden, who was among the first to oppose it, appears 



