88 



VEGETABLE HISTOLOGY. 



Apply chlor-zinc-iodine. The cell-walls stain blue and the 

 contents a brown, showing presence of albuminous matter. 

 Alcannin or cyanin solutions would show the presence of oily 

 or resinous matters. These are held in suspension by emulsion 

 and give the latex the milky appearance. 



COMPLEX OR BRANCHING LATEX TUBES. 



These occur in a number of plants, for example, Dandelion, 

 Chicory, Celandine, Poppy, etc. 



Make cross-sections of Dandelion and Chicory roots, stain 

 with hsematoxylin so- 

 lution and wash thor- 

 oughly in water. 



The milk cells are 

 arranged in small 

 groups, and these form, 

 in the Dandelion, con- 

 centric circles through- 

 out the whole bark, 

 which, to the naked 

 eye and under low 

 power, seem complete. 

 Under high power the 

 circles are interrupt- 

 ed here and there. In 

 Chicory the milk tubes 

 are arranged in radi- 

 ating lines through the 



Fig. 53. Longitudinal radial section of Chicor 

 root, showing branching latex tubes, sc 

 (Moeller). 



bark, and by means of 



the milk tubes alone 



Dandelion and Chicory 



can readily be distinguished under the microscope. The milk 



cells stain more deeply than the surrounding parenchyma cells 



and thus stand out conspicuously. 



Study longitudinal radial section of Dandelion and longitu- 

 dinal tangential section of Chicory. 



The milk ducts form a tangled network in the elongated 

 parenchyma cells of the bark of the root. There are numerous 

 cross-branches connecting the tubes. 



