THE PRINCIPAL TISSUES. 77 



(2.) The other form is that composed of reticulately anas- 

 tomosing vessels. Here the tissue is the result of the fusion 

 of great numbers of short cells. The walls are thin and 

 often irregular in outline. In Cichoriacece this form of 

 laticiferous tissue is very perfectly developed as a consti- 

 tuent part of the phloem portion of the fibro-vascular 

 bundles (Fig. 65, A and B}. 



(a) Laticiferous tissue has not yet been shown to contain either pro- 

 toplasm or nucleus.* The latex is an emulsion of several substances, 

 some of which, as caoutchouc (India-rubber), gutta-percha, and opium, 

 are of great economic importance. In some cases, as in Euphorbia, 

 grains of starch are contained in the latex (Fig. 64, B). 



(b) The chemical composition of latex is shown by the following 

 analyses, as given by De Bary: f 



Latex of Hevea Guianensis. as determined by Faraday : 



Water with an organic acid 56.3 per cent. 



Caoutchouc 31.7 " " 



Albumen 1.9 " " 



Bitter nitrogenous matter, with wax. 7.1 " " 



Residue soluble in H 2 O, but insoluble in alcohol. 2.9 " " 



999 



Latex of Qalactodendron uttte, as determined by Heintz : 



Water 57.3 per cent. 



Albumen 0.4 



Wax (C 35 H 66 O 3 ) 5.8 



Resin (C 36 H 68 O a ) 31.4 



Gum and sugar 4.7 



Ash 0.4 



100. 



Latex of Euphorbia cyparissias, determined by Weiss and Wiesner : 



Water 72.1 per cent. 



Resin 15.7 



Gum 36 



Sugar and extractive substances 4.1 



Albumen 0.1 



Ash 0.9 



96.5 



of the xylem assume the form and function of laticiferous vessels.", 

 Sachs' " Text-Book of Botany," English edition, p. 110. 



* The latex of some Cichoriacese coagulates much like protoplasm : 

 possibly further investigation will show it to be present. 



f "Anatomic der Vegetationsorgane," etc., p. 194. 



