42 THE TISSUES OF PLANTS 



(m) For the study of latieiferous tissue thin tangential 

 sections are best. The tissues will show as tubes filled with a 

 brown granular mass, the latex. The non-anastomosing type 

 can be found in the milkweed (Asclepias), dogbane (Apo- 

 cynum), and spurge (Euphorbia), especially the more fleshy 

 forms of the latter. The anastomosing type can be studied 

 in the petioles of dandelion or lettuce, or in the stem of the 



poppy- • . , . -, X I, 



(n) The long, branching, non-anastomosmg latieiferous tubes 

 of Euphorbia can be isolated from the more fleshy leaved sorts 

 by boiling the leaves in dilute potash solution and then teasing 

 out a piece of the softened tissues. By a similar treatment 

 of the peduncle of the dandelion the anastomosing latieiferous 

 tissue may be studied. 



(o) To examine the tissues in situ, the leaves should be 

 placed in strong alcohol (90-95%) for some hours. If the 

 leaves are thick, thin sections should be made parallel to 

 the surface. These sections, or the whole leaves if they are 

 thin, should then be placed for an hour or so in a clearing fluid 

 made of equal parts of turpentine and carboUc acid (phenol). 

 Mount the section or leaf in this fluid. The tissues are made 

 transparent, and the latieiferous tubes filled with granules of 

 latex can be studied with great ease. The same method can be 

 used for studying both types of latieiferous tissue. 



REFERENCE BOOKS 



The books enumerated for Chapter I and the following. 

 A. DeBary, Comparative Anatomy of the Vegetative Organs of 



Phanerogams and Ferns (Engl. Ed. 1884. Oxford). 

 G. Haberlandt, Physiologische Pfianzenanatomie, Leipzig, 



1904. (Engl. Ed. 1914. London.) 



