3 16 Schively — Contributions to the Life History of 



the bladder form are abundant; the former is tuberculate 

 in character. 



In a transverse section of the pulvinus the flattened por- 

 tion indicates the dorsal region. The epidermis is strongly 

 cuticularized ; in the many celled cortex there are few 

 chlorophyll granules. Numerous crystals of the character 

 previously mentioned as occurring in the stem are found ; 

 the number is variable, but nearly all exhibit the twin 

 arrangement more plainly than is usually seen in other 

 parts of the tissue. In the secondary and tertiary pulvini 

 the crystals are comparatively more numerous. 



In the fundamental tissue, lying next the central mass, 

 the cells are similar, and possess somewhat thicker walls. 



The cells of the bundle-sheath resemble in appearance 

 those in the centre of the pulvinus, and show clear collen- 

 chymatous walls. Chlor-iodide of Zinc produces a violet 

 coloration. Next to the sheath lies the phloem ; then the 

 xylem which occupies a relatively large area. Chlorophyll 

 is very abundant just within the bundle sheath. 



All the usual reagents reveal the presence of tannin cells 

 in the xylem. 



Continuity of protoplasm is best demonstrated in the 

 phloem region and the central mass of collenchyma. 



Clear refractive globules have been observed in the 

 cortex ; these do not consist of oil, nor of tannin, for treat- 

 ment with special reagents to demonstrate the presence of 

 either substance, yields no satisfactory results. Their com- 

 position has not yet been ascertained. They are not always 

 seen, and from a few observations which have been made, 

 I think their presence has some connection with the posi- 

 tion of the leaf at the time when the study is made ; but 

 whether they are most abundant during the normal, the 

 para-heliotropic or the nyctitropic position can not yet be 

 definitely stated. 



These globules which appear to be absent in the secon- 

 dary and tertiary pulvini, may be distinguished in the 

 primary. 



