214 BOTANICAL GAZETTE [September 



short, the transition from stem to root taking place in an almost hori- 

 zontal plane (fig. 30). In the absence of cauline bundles, the root 

 poles are inserted upon the cotyledonary strands (A, B, C, D, figs. 

 34, 35). There is no rotation of the protoxylem, but the phloem and 

 metaxylem separate opposite the protoxylem groups (Bn, Cn, fig. 

 36), the cambium proliferating to fill the breach in the metaxylem, 

 and the cortex invading the space left vacant by the phloem. The 

 resulting halves swing, the one to the right, the other to the left, giving 

 the appearance of a double fan of phloem and metaxylem connected 

 by a single group of protoxylem. The right half of the phloem of 

 one pole joins the left half of that of the next, and the cambium layer 

 is thus curved inward (cb, figs, jy, 38). One result of this compli- 

 cated process is that the entire xylem system of the root is bordered 

 peripherally by cambium. 



The medulla throughout the root is extremely meristematic, and 

 its activity sometimes results in a displacement of one or more of the 

 protoxylem groups, giving an unsymmetrical appearance in cross- 

 section. This activity is indicated by the thin walls (0, fig. 38) 

 showing recent division. 



In all the plants I have investigated, the number of poles remains 

 constant throughout any given root. This number may be three or 

 four, depending seemingly upon the degree of development attained 

 by the median bundle of the aborted cotyledon. Figs. 26 and 34 

 will serve to illustrate this point. They represent the same level 

 in two different plants. In the former the median bundle (D) was 

 very weak, and there were but three root poles; in the latter this 

 bundle was well developed and the root was tetrarch. 



Fig. 3Q represents the condition of the root tip in the region of 

 the differentiation of protoxylem. The connective tissue is clearly 

 defined, but there is no xylem plate connecting the poles. Examina- 

 tion of longitudinal sections of the root tip furnishes nothing that could 

 be added to the description of Reinke (10). One initial group pro- 

 duces plerome, another periblem. There is no calyptrogen or der- 

 matogen, but the outermost layers of the periblem become loosened 

 at the tip and form the root cap (k, fig. 42). 



There is no distinct endodermis, and the pericycle is several- 

 layered, making it impossible to distinguish with absolute cer- 



