88 PEACTICAL BOTANY. 



The main constituents of the tissues are parenchy- 

 matous 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 network of laticiferous 

 vessels. The communication of these tubes with 

 one another is demonstrated by the continuity of 

 their contents (latex), which appear brown and 

 granular. 



The course of the vessels is mainly longitudinal, 

 while lateral, horizontal branches frequently connect 

 the parallel tubes. 



With a high power make out more accurately the 

 course of a group of the vessels. 



II. Cut transverse sections of the same ; mount in 

 glycerine, and examine with a low power. 



The laticiferous vessels appear circular in transverse 

 section, and have brown contents ; they are distributed 

 in groups, which form more or less regular concentric 

 rings round the central xylem. 



Note in these sections the presence of sphere 

 crystals of Inulin. In the former section they will 

 have been dissolved by the treatment with potash. 

 Observe that they are formed quite irrespective of 

 the cell-walls, which are often included in them. 



Treat the sections with iodine solution. They are 

 not definitely stained. 



Run some potash under the cover slip. They will 

 be gradually dissolved without swelling. 



The development of tlie laticiferous vessels may be traced by 

 cutting thin longitudinal sections through the cambium of the 

 root of the Dandelion. By careful comparison of such sections it 



