LATICIFEROUS VESSELS 73 



LATICIFEROUS TISSUES 



The material for the study of these tissues should be prepared 

 by treatment with alcohol to coagulate the latex. Care should 

 be taken to place the material in alcohol directly it is cut, or 

 at least the cut surfaces should be wetted with alcohol so as to 

 check the flow of latex from them. If the latex be allowed to 

 escape, the laticiferous tissues are emptied, and are then much 

 less easily traced than when they are full. The best method 

 is perhaps to preserve the whole plant without injury in 

 alcohol, in which case the latex will not be lost at all. 



Draw from a piece of the fresh stem of Euphorbia a drop of 

 latex upon a slide : examine it quickly under the microscope, 

 and observe the fluid is at first almost uniformly milky, but 

 that in a short time a coaguluxu separates in irregular masses 

 from the more transparent fluid. The coagulation is effected 

 more completely and rapidly on addition of a drop of 

 alcohol. 



i. Laticiferous Vessels. 



I. Cut tangential sections from the phloem of the root of 

 the Dandelion (Taraxacum officinale), mount in potash and 

 glycerine, and warm ; examine under a low power. 



The main constituents of the tissues are parenchymatous 

 cells, with thin walls (phloem-parenchyma) : sieve-tubes are to 

 be met with here and there. The whole mass of tissue is 

 permeated by a ramifying and profusely anastomosing net- 

 work of laticiferous vessels. The communication of these 

 tubes with one another is demonstrated by the continuity of 

 their coagulated contents (latex), which appear brown and 

 granular. 



The course of the vessels is mainly longitudinal, while 



