252 THE ANATOMY OF STEMS. 



in some instances of a dark color, and in others white, 

 dispersed over a white or a green ground, in the order 

 just described. The epidermis adheres closely to the 

 parenchyma beneath it ; and in some plants of this 

 class, the greater density of the cellular substance at 

 the circumference gives the appearance of a bark, 

 which is never, however, present in this description of 

 stem. Such is the general character, and the distri- 

 bution of the parts, in what may be termed the ligne- 

 ous solid monocotyledonous stems ; but when they 

 have more of an herbaceous character, such, for ex- 

 ample, as the scape of the great yellow Garlick {Allium 

 Moly) and other species, there are no indurated lig- 

 neous cords ; but the vessels run in the midst of lon- 

 gitudinal layers of condensed cellular matter, and in a 

 transverse section appear as white dots forming a rir- 

 cle round the central cells, which are generally much 

 larger than those of the circumference, and assume 

 in some degree the aspect of a pith ; so that in the 

 longitudinal section, the diameter of the stem appears 

 divided by two seemingly solid cords, into three nearly 

 equal compartments. 



Such are the appearances which, to the naked eye, 

 or to the eye aided by a common lens, the solid mono- 

 cotyledonous stems present. Under the microscope, 

 we perceive that each ligneous cord is composed of 

 very narrow oblong cells, and of vessels which are 

 either spiral, annular, or porous, those in the centre 

 being always spiral : that, in the cellular substance of 

 the more solid stems, the cells are chiefly oblong, 

 whilst in that of the herbaceous they form irregular 

 hexagons, except towards the circumference, and in 

 the immediate vicinity of the vascular cords ; and that 

 the membrane forming them is perforated with minute 

 pores, surrounded by a glandular border. 



