divers: Xofcs on Yorksliirc Ihyophytes. 



3^9 



The t'ung'us was found to extend throuj^hout the wliole of the 

 lower portion of the stem, but in the upper expanded portion it 

 is confined to a ventral zone immediately within the superficial 

 layer of cells (Fig-. 2). The hyphae were frequently seen to 

 traverse the rhizoids and penetrate the inner cells, in which 

 they become branched and coiled in an intricate manner, often 

 entirely filling' the cell-cavity. Here and there the hyphce bear 

 swelling's, but the vesicles are not nearly so larg^e as in the fung^al 

 zone or mycorhiza of the Marchantiaceae, e.g". , Fegatella, Prcissia. 



Fij. 2. — I. -III. Successive transverse sections of the stem, x 20; m, niycorhizal 

 zone. IV. Part of I., X 50, showing' fungal hyphffi traversing the rhizoids and 

 ramifying in cells of mycorhizal zone. V. Two cells containing hyphae, x 3,^0. 



In passing- towards the upper or leaf-bearing- region, the 

 stem becomes flattened above and below, with an oval cross- 

 section, the rhizoids at the same time becoming- confined to the 

 lower surface (Fig-. 2, II., III.). Further upwards, the lateral 

 wing-s appear as horizontal outgrowths, level with the flattened 

 upper surface of the stem, of which they are simply lateral 

 expansions. These wings consist for the greater part of three 

 or four layers of cells, thinning out at the margin to a single 

 layer. The wings increase in breadth from behind forwards 

 and then diminish again towards the anterior end of the shoot, 

 where there is a shallow notch occupied by the apical growing- 

 point. In the apical region, the lower surface of the stem bears 

 numerous small scales, arranged in two longitudinal rows ; each 



1903 September i. 



