114 



MINNESOTA BOTANICAL STUDIES. 



A definite endodermis was not distinguished at any stage, al- 

 though, since starch is present in the region of the pericyle and 

 endodermis from the first, those regions can be located approx- 

 imately. Starch is found later in pith and cortex ; also in many 

 of the inner xylem elements. 



There are, at first, eight to ten conjoint vascular bundles. 

 Eventually the phloem and xylem form closed rings. 



Scattered sclerenchymatous elements are found in the phloem, 

 pericycle and cortex. 



The pith is irregular in outline. The first formed xylem ele- 

 ments project into it. The perimedullary zone is not conspic- 

 uous the first year, being composed of a few cells with unligni- 

 fied walls. 



The cork cambium is formed in the outermost hypodermal 

 layer (cf. Moeller [1882], p. 327). 



Comparison of Structure of Hypocotyl and Epicotyl. 



The hypocotyl has a few, the epi- 

 cotyl a considerable number, of epi- 

 dermal hairs. The hypocotyl does 

 not have the collenchymatous hypo- 

 derma found in the epicotyl. The 

 pith is smaller and circular instead 

 of scalloped ; the perimedullary zone 

 is better developed. 



The endodermis is distinct in the 

 hypocotyl for a considerable time, 

 while in the epicotyl it was not 

 definitely distinguished at all. The 

 hypocotyl has, at first, four xylem 

 and four phloem bundles ; the epi- 

 cotyl eight to ten conjoint bundles. 



At the close of the year the only dif- 

 ferences are those noted in the me- 

 dullary and perimedullary regions. 



Ailanthiis 

 glandulosa 



FIG. 14. 



ANACARDIACE^E. 



Schinus molle. 

 Structure of Hypocotyl. 



The epidermal cells are square or oblong in cross section, 

 becoming, at length, flattened. There are numerous short epi- 



