Manchester Memoirs^ Vol. Ivii. (£913) No, IG. 5 



On the other hand, the series of laj^ers of the root-cap 

 is rather suggestive of these having been cut off seriatim 

 from a single apical cell. It will be seen that the root-cap 

 is very massive, and extends a considerable way back 

 from the apex. In the section under consideration the 

 cells of the root cap have become much compressed and 

 blackened, probably due to their disorganisation, except 

 near the root-tip, where they are distinct and can be seen to 

 be of large size. On another root tip {^Fig. 2), where they 

 are better preserved, the cells can be seen to be two to 

 three times the diameter of the meristematic cells and 

 many times the length. 



Among the more numerous transverse sections 

 through young root, the one represented in Ftg. 3 is 

 so close to the apex that it includes the remains of 

 the disorganised root-cap to the outside. Only "15 mm. 

 in diameter, it occurs on a slide (R. 617), crowded with 

 remains of Lyginodendron roots of all ages. The trans- 

 verse section of this root apex shows four very distinct 

 external layers of cells, which can readily be identified 

 with the corresponding tissues of the older roots. The 

 outermost two layers, consisting of large cells closely set 

 together, are the two characteristic layers of the Lygino- 

 dendroti roots, called exodermis by Scott. The outermost, 

 as will be seen from an examination of the longitudinal 

 sections, might be considered to be of epidermal nature. 

 The third layer, from the brown contents of some of its 

 cells, can be easily identified with the inner cortex. On 

 the inside of this tissue small intercellular spaces can be 

 observed in some parts of the section. Next comes the 

 endodermis, composed of six very clearly defined cells. 

 The number and very regular arrangement of these cells 

 reminds one of the condition of young fern roots, and is 

 very suggestive of the origin of the tissues from a tetra- 



