Development of Cassytha fil-iformis, L. 411 



vessels are normally quite empty. Through their bordered 

 pits from the adjoining smaller cells, hernioid protoplasmic 

 swellings protrude, which even in the earliest stages show a 

 delicate wall. This phenomenon is so frequent that one can 

 scarcely cut a section without finding at least one instance 

 of it. Not only the bordered pits, but apparently any of the 

 pitted elements show it. The small undifferentiated wood 

 cells are rich in protoplasm and contain healthy nuclei. 

 They communicate with the large pitted vessels by the 

 closely packed pits. One cell may have as many as six such 

 openings, and through each of these the protoplasm may 

 ooze. There is apparently no regularity, as the figures 

 demonstrate. Frequently the entire nucleus, which in such 

 cells always lies on the side by which the protoplasm is 

 escaping, squeezes its way through the much smaller pit, 

 and when it is through, again rounds out to its normal form. 

 The entire vessel may thus be completely blocked by immi- 

 gration of cells, which have nucleus and cell wall, though 

 this latter seems of a highly plastic nature, being round when 

 not impeded, but admitting of indentation by other buds 

 that may come in contact with it. The small pitted cells 

 into which tyloses form show no large connection between 

 their ends, while the pits are oval, not bordered. 



The protoxylem shows the usual spiral tracheae. 



The leaves are small, scale-like and comparatively func- 

 tionless. They are scattered and occur in a one-third spiral, 

 six to eight cm. apart. The young green seedling has green, 

 sessile scales, one to one and a half mm. long and with a 

 broad attachment. They have stomata on both surfaces 

 and are supplied with three veins. Some have long jointed 

 hairs on their edges, probably surviving remnants rather 

 than functional organs. The older leaves lose their green 

 color, become quite membranous and dried at the tip, but 

 retain their stomata. 



In the seedling stem the earliest distinguishable trace of the 

 stelar system is a ring of five xylem elements, each asso- 



