CANNABIS SATIVA Z3i 



primary phloem group by the time that secondary growth is 

 initiated. The ducts are ephemeral; and, together with other 

 elements of the protophloem, become crushed against the pericycle 

 as secondary growth proceeds. 



Of the primary xylem, three to five thin-walled annular and 

 spiral elements constitute each protoxylem point. The outermost 

 and smallest of these abuts the inner layer of the pericycle, which 

 is three or four cells in width by the time the first annular vessel is 

 mature. The other protoxylem elements are bounded laterally by 

 regions of fundamental parenchyma in which cambial activity 

 is later initiated. The metaxylem elements continue to mature 

 centripetally so that the primary xylem strand is complete at a 

 level about 0.6 mm. above the root tip. The metaxylem vessels 

 have distinctly bordered pits in which the borders are narrow and 

 the torus thin. Scalariform vessels may rarely occur. 



A rather unusual case of tetraploidy in the primary root has 

 been reported by de Litardiere (19) and Breslawetz (5). The 

 diploid number of chromosomes in hemp is 1.0 and this obtains 

 for the cells in the plerome, but both investigators found the 

 tetraploid number of 40 in the cells of the periblem. This situation 

 was observed by de Litardiere in specimens selected from two 

 varieties of hemp grown in different localities; and, coupled with 

 the confirmatory report of Breslawetz (5), would indicate that 

 the condition is general rather than aberrant. Several explanations 

 have been advanced to account for it. Breslawetz attributes it to 

 the occurrence of nuclear divisions in the cells of the periblem 

 which are not followed by cytogenesis, but, instead, by the enlarge- 

 ment of the cells involved and by the fusion of the two nuclei in 

 each cell. On the other hand, de Litardiere did not encounter 

 any binucleate cells, and suggests that the situation may arise 

 from a normal metaphase followed by a monocentric telophase 

 which would produce a single tetraploid daughter nucleus. This 

 same phenomenon has also been reported by de Litardiere (18) 

 and Langlet (17) for Spinacia. The latter, however, did not 

 agree with de Litardiere in respect to Cannabis sativa, as he found 

 tetraploid cells abundant in all tissues of its root tip. 



The Formation of Lateral Roots. — The primordia of lateral 

 roots arise early in the ontogeny of the primary root at about the 

 time the protoxylem begins to mature. As a result of divisions of 

 the pericyclic cells in three planes, conical growing points are 



