04 PROCEEDINGS OF SOCIETIES. 



ordinary conifers, but the central dot is replaced by an elliptical opening, 

 exactly the same as the peculiar central markings found in the punctated tissue 

 of the Cycadacece. The presence of medullary rays, the uniform size of the 

 cells, as seen on transverse section, and the presence of punctations, although 

 they are peculiar, seem all to point to a close relation to tlie ConifercE. As I 

 cannot refer the Lignite to the carboniferous genera, Dadosylon or Dictyoxylon, 

 it seems possible that it will have to be referred to a new genus ; if so, I would 

 venture to suggest the name of Palceopitys MiUerii, for the Old Red Sand- 

 stone Lignite now described. II. Histological Notes. By W. R. M'Nab, 

 M.D., Edinburgh. 1. On the Structure of the Adventitious Roots of the 

 Portugal Laui'el. They arise in patches, more or less large, from the branches, 

 but not in any regular order, their position on the branch not giving any clue 

 to their relative age. The bark was always ruptured and pushed aside by the 

 rootlets, showing that they have a deep-seated and not a superficial origin. 

 The only difference between these adventitious and true roots is in their posi- 

 tion and irregular mode of growth. In their growing by addition to the 

 growing point, and in histological charactei's, they are undistinguishable from 

 true roots. Root hairs were also produced iu abundance by tlie epidermis. 

 2. On Intercellular Substance and Cuticle. Careful observation of the growth 

 of cells in the young roots of the white Mustard, Phalaris canariensis, andtlie 

 garden Pea and Bean, have led to the conclusion that the so-called intercellular 

 substance is, in reality, the original or primary cell-wall — that as growth goes 

 on, tliis primary cell- wall becomes thickened by the addition of numerous more 

 or less marked layers on the inside. In the stems of many plants it requires 

 some care to be able to demonstrate that the cell- wall and thickening layers are 

 separate. In the layer of cells of the epidermis, on wliicli the cuticle rests, 

 the outer surface is in general greatly thickened, while the inner part of the 

 cells are only thickened at the angles at which the other cells join. Tliis 

 thickening at the angles is often so great that the cell a^jpears almost filled up, 

 or the thickening appears as a continuous layer. In the epidermal and sub- 

 epidermal cells of the Ivy the thickening is so great that without careful 

 examination the thickening might be considered continuous. , On tiie more or 

 less thickened external surface the cuticle rests, and may be considered as 

 thickening occiu'riug outside the cell-wall. From the observations made, the 

 statements of Wiegaud, Schacht, and others, regarding the identity of inter- 

 cellular substance and cuticle, were considered untenable. III. Notice of 

 Jlieracium stolonijlorum, Waldst. and Kit. ; H. glomeratum, Fr. ; H.prcealtum, 

 Vill., as occurring in the neighbourhood of Edinburgh. By Professor Balfour. 

 Professor Balfour gave descriptions of the above thre"B species of Rieraclum, 

 which had recently been met with, growing in a wild state in the neighbourhood 

 of Edinburgli. S. fraaltum, was collected by Dr. John Kirk, in 1854, near 

 Kincardine, in Fife ; H. glomeratum, by Mr. John M'Laren, in June, 1869, 

 growing on railway banks between Edinburgh and Granton ; and H. stolonl 

 florum, collected by himself and Mr. Sadler, in October, 1869, on the railway 

 banks between Warriston and Trinity.* Specimens were exhibited and pre- 



* See ' Journal of Botany,' Vol. VII. p. 337. 



