CANNABIS SATIVA 2.39 



than the caliber of the remainder of the tube. The phloem fibers 

 are smaller, shorter, thinner-walled, and more brittle than the 

 pericyclic fibers. They occur in zones in the phloem, either singly 

 or in groups. In the older portions of the stem, continued second- 

 ary thickening may result in the formation of successive zones of 

 fibers, giving the phloem a banded appearance. 



The ducts are apparently unique for the Moraceae, as they differ 

 from the unsegmented types found in the Asclepiadaceae and 

 Euphorbiaceae in being unbranched, and in their manner and point 

 of origin. They are also unlike the latex vessels of Papavaraceae, 

 Cariaceae, and Musaceae, since they are not formed from a longi- 

 tudinal series of cells by the absorption of their end walls. Zander 

 (30) has described the structure and development of the ducts in 

 detail, and notes that they are unbranched, unicellular, and multi- 

 nucleate. They do not occur in the root, cotyledons, or greater 

 part of the hypocotyl; and are not similar in their ontogeny to the 

 primary phloem ducts found in the primary root. 



In ontogeny, the ducts first appear at the time of the differentia- 

 tion of the first leaves above the cotyledons. They occur in the 

 primary phloem of the median bundle of the leaf, and are differen- 

 tiated downward through the cotyledonary node and into the upper 

 portion of the hypocotyledonary axis. Additional latex ducts 

 arise in the same manner at the tips of the vegetative axes as the 

 subsequent leaves are differentiated. (Fig. 115.) The initials of 

 the latex ducts are round or oval when first distinguishable in 

 the growing point and in the leaf primordia. The lumen of the 

 duct is larger than that of the adjacent cells and the cell wall is 

 somewhat thicker. They contain a golden-brown granular sub- 

 stance and have spindle-shaped nuclei that are larger than the sub- 

 spherical nuclei of the adjacent parenchymatous cells. 



As the leaf and axis develop, the latex ducts become long, sinu- 

 ous, unsegmented canals which may attain an extraordinary 

 length. Zander observed ducts which extended through more than 

 one internode of a mature plant exceeding 30 cm. in length. In 

 no instance was there any indication of either branching or anas- 

 tomosing, and he concluded that each one was an independent struc- 

 ture. They occur in the outer limits of the primary phloem, and 

 the number of ducts in transections of stems, varying in age from 

 very young seedlings up to mature plants over 3 meters in height, 

 reveal no significant differences. Zander concluded from this that 



