C. U. C. p. ALUMNI JOURNAL 



157 



the fiber. Cubical crystals and frag- 

 ments of the latter are seen in abund- 

 ance; also reddish-brown fragments of 

 cork tissue and resin masses are dis- 

 tributed throughout the field. ]\Iany 

 vessels are present. 



The most important differences in 

 Asclepias syriaca are the stone cells 

 which are pale to light yellow in color. 

 They are deeply pitted and non-striated 

 .15 to .48 millimeter in length and .06 to 

 .15 millimeter in width. 



Rosette crystals are next in promi- 



nence and . vary in size from .06 to .20 

 millimeter. Wood fibers and other ele- 

 ments similar to Asclepias tuberosa are 

 also seen. 



The stone cells in Asclepias decum- 

 bens are almost triangular. The major-* 

 ity are .25 millimeter long and .25 milli- 

 meter wide with much thicker walls 

 than asclepias syriaca with smaller cavi- 

 ties, non-pitted but striated. The starch 

 is larger and more abundant. Many 

 cubical crystals, but few rosettes are 

 present. Other elements are similar to 

 Asclepias tuberosa and Asclepias syriaca. 



Comparison of Histological Characters. 



Comparison of Gross Characters. 



