Ramaley: anatomy of onagraceae. 681 



perhaps, 100 or 200mik. ; sometimes they are 1 to 2mm. In 

 Oenothera humifusa many of the hairs are placed upon large 

 multicellular emergences. This occurs occasionally also in 

 some of the other species. Besides the usual long, straight or 

 slightly curved hairs there are often present short clavate 

 ones, not much longer than the epidermal cells, e. g., Galpinsia 

 hartwegii and Oenothera sinuata. 



Sub-epidermis. — This consists usually of a narrow zone of 

 collenchyma enclosing a greater or less amount of parenchyma. 

 In some cases the cells of the first one or two rows below the 

 epidermis might, perhaps, be best described as sclerenchyma. 

 They resemble very much, when seen in cross section, the 

 epidermal cells. Occasionally there is but one such row, so 

 that the epidermis appears two-layered. In no case is the col- 

 lenchyma greatly thickened at the angles. The collenchyma 

 usually, though not always, shades gradually into parenchyma. 

 In Oenothera humifusa, and, at times, in other species, there 

 is but a single layer of thick- walled cells within the epidermis. 

 This species is also remarkable for its numerous large emerg- 

 ences, at the bases of which are often situated crystal sacs. 

 Emergences commonly, however of smaller size and fewer in 

 number, are found in all the species examined. These, as a 

 rule, seem not to offer communication with the outside world, 

 but are simply irregular thickenings of the cortical layer. 



The cells in both the collenchymatous and parenchymatous 

 portions are somewhat flattened in the plane parallel to the 

 epidermis. When seen in cross section they are often twice as 

 long as broad. There is considerable difference in the thick- 

 ness of the parenchymatous zone, depending upon the species 

 and the particular plant examined. Sometimes this zone is 

 but a very few cells broad, e. g., in Kneiffia fruticosa, where 

 the whole sub- epidermal area is, for the most part, poorly 

 developed. 



Cells containing raphides of calcium oxalate are commonly 

 abundant in the parenchymatous tissue. This is especially the 

 case in those stems in which the cortical parenchyma is well 

 developed. It is to be noted that the crystal sacs are not dis- 

 tributed evenly along all parts of the stem, but are very irreg- 

 ular as to their occurence. A cross section of the stem taken 

 at a certain height may contain but a few crystallogenous cells, 

 while one taken a millimeter above or below it may show them 

 in great abundance. These cells are commonly of considerable 

 size, nearly circular, in cross section about 30 to 40mik. in diam- 



