LATICIFEEOUS TISSUE OP MANIHOT GLAZIOVII, 199 



In tangential sections of younger portions of the stem, in 

 which the primary phloem is still in course of development, the 

 origin of the anastomosing knots mentioned above may be 

 traced. One or more of the parenchymatous cells lying 

 between two bands of laticiferous vessels becomes divided up 

 by transverse walls into a number of narrow cells. The ter- 

 minal walls of these cells, Avhere they abut on the main trunks 

 of the vessels, become wholly or partially absorbed, and the 

 same is the case with large portions of their horizontal walls. 

 A complicated system of communicating passages is thus 

 produced (fig. 4). 



Very complicated anastomoses also take place at the points 

 of junction of the meshes formed by the laticiferous vessels. 

 At these places a large number of vessels are in contact, and 

 they may all have the longitudinal walls separating them 

 absorbed, at numerous points, only quite narrow bands of 

 cellulose being left between the perforations. 



As regards the period at which perforation of the walls takes 

 place, two facts may be mentioned which illustrate the close 

 similarity between the laticiferous tissue in Manihot and that 

 in the Cichoriacese. The first point is that cross-walls may be 

 found still completely preserved, where large perforations in 

 the lateral walls already exist (cf. fig. 3). Among the Cicho- 

 riaceee it was noticed by Schmalhausen ^ in the case of Trago- 

 pogon, that the lateral walls are perforated before the trans- 

 verse ones, and this observation I was able to confirm in most, 

 if not iu all cases.- Secondly, in Manihot, as in the Cicho- 

 riaceee, latex is present before the cross-walls are absorbed.^ 



The lateral walls of the laticiferous vessels are often much 

 undulated, the protrusions and depressions fitting into one 

 another where two vessels run side by side. It follows that 

 after perforation has taken place, the remaining portions of the 



Mr. W. Gardiner for calling my attention to this reagent, and for other 

 practical suggestions. 



1 L. c. 



» See vol. xxi of this Journal (1SS2), p. 147. 



3 Ibid., p. 153. 



