Manchester Memoirs, Vol, xli. (1896), No. 3 



produced into hair-like processes, attaining a length of 

 •25 mm. (Fig. 1, H.). These do not appear to be cut off 

 by a cell wall from the cells from which they arise. The 

 walls of these hairs, and also of the cells of the basal part 

 of the stalk, differ slightly in composition from the corky 

 cell walls, as on treating with iodine and sulphuric acid 

 they stain slightly bluish-green, but do not swell appre- 

 ciably. These cell walls appear to be cellulose which has 

 become almost transformed to cork. The hairs are 

 probably the remains of absorbing organs (the rootlets 

 mentioned in the Synopsis) which performed some 

 function during the formation of the tuber. 



Within the protective cells, lie closely-packed cells 

 which all contain food materials. The cell walls of this 

 portion of the tuber are thin, and of unchanged cellulose 

 (PL 2, Fig. 2). Each cell contains a large, central, 

 usually elongated nucleus (N), a large number of round 

 or oval granules (G), colourless or slightly yellow 

 imbedded in the remains of the protoplasm (P), and 

 numerous small oil drops (O), or one large one due to 

 the coalescence of the smaller drops. 



The oil is present in considerable quantity, as can 

 readily be seen on crushing a tuber in water between 

 a glass slide and a cover, when large fluid oil-drops exude. 

 These are at once stained brown, or black, by osmic 

 acid. The drops are readily soluble in chloroform, ether, 

 benzene, but dissolve only slowly in absolute alcohol. 

 The oil is not vaporised by heating for two hours to 

 120 0 — i40°C, and it is not readily saponified with 

 potash, even on heating for several minutes. The oil- 

 drops are fluid at the ordinary temperature (i2°C), as 

 can be seen on compression. 



The granules present in the cells are of different sizes 

 (Fig. 2); a few are large, but the greater number are of 

 smaller size. The larger granules have an average diameter 



