1908] DORETY—CERATOZAMIA 215 



tainty any line of demarkation between phloeoterma and stelar 

 tissue. 



There are no anomalous thickenings in the roots of plants two 

 years old. 



In general, mucilage ducts extend but a slight distance into the 

 root, usually about 8 mm , but in one specimen they were beginning to 

 be formed in the plerome, immediately behind the region of its differ- 

 entiation (md, fig. 42). 



The lateral roots are diarch. Fig. 40 represents a transverse sec- 

 tion of a secondary root and the exit of a tertiary one. The upper- 

 most lateral roots become ageotropic at a very early stage, and show 

 symptoms of bacterial infection; and in some of the two-year-old 

 plants, these roots present the characteristic "coralloid" appearance 

 indicative of algal infection. 



The root, as was seen above, is late in developing. Fig. 27 

 represents the position and form of the meristematic plate, which 

 has given rise to stem above, but is yet inactive below. Fig. ig shows 

 the beginning of the activity which produces the root; the central 

 portion of the active region in this figure is sketched in greater detail 

 in fig. 41. In the stage represented in fig. 42, the root cap is devel- 

 oped and the plerome and periblem initial groups are easily distin- 

 guishable, but the plerome has not yet differentiated any xylem 

 elements. 



While in older seedlings the vascular systems of stem and root seem 

 to be continuous, one sometimes finds sections which indicate a certain 

 amount of interruption. Such a case is shown in fig. 4J. 1 



Discussion 



The result of the experimental work on Ceratozamia places this 

 genus in line with the other cycads with reference to the dicotyledonous 



1 When this investigation was completed, Matte (7) published a preliminary 

 note on the same subject. He says that the petiolary bundles have the & arrange- 

 ment, that there is an anterior fascicular system in the region of insertion of the rachis, 

 and that the pinna has terminal teeth. These features do not appear in any of my 

 seedlings. Speaking of the root, he says it is tetrarch, and that he has observed a 

 progressive reduction of poles, to three and even to two. As I have observed, no 

 reduction occurred in the roots of any of the seedlings I sectioned, and the root is 

 triarch as often as it is tetrarch. He has also found the abnormal thickenings strongly 

 developed; but he does not give the age of the seedlings which manifest them. 



