414 Boewig on the Histology and 



Subsequent growth causes elongation of all epidermal 

 cells, so that in older portions these sister cells no longer 

 project above the surface. After spreading out, the stomatic 

 cells flatten somewhat and lay down thickening on their 

 outer face. This thickening assumes a slanting position 

 (Fig. 12, d). The separation of the two stomatic guard 

 cells, especially at their more internal portion, their further 

 flattening and increased thickening of the upper wall, com- 

 plete the formation of the stoma. Young stomata, even 

 when completely formed, have no intercellular space beneath 

 them. It is not at all unusual to find two or three stomata 

 in a row, but they are always separated by two cells — the 

 sister cells just described. Laterally consecutive cells do not 

 form stomata. They are strictly in rows. The furrowing 

 of these rows is not evident in young stems, and is a sec- 

 ondary development, apparently due to the greater expansion 

 of parts not in line. This is further borne out by the hol- 

 lowed appearance of the furrows. The cells do not sink 

 abruptly, but are merely concave. 



As will be seen from the highly organized stem system, 

 this plant, while a typical parasite in many respects, cannot 

 be said to have been much degraded in its stem histology. 

 The extensive xylem system of the stem and branches, and 

 its high organization of elements, as well as the abundant 

 stomata and large amount of chlorophyll, indicate that the 

 plant absorbs crude sap from its host and does much of its 

 own elaborating. This position is further fortified by the 

 structure of the haustoria, which show well-developed and 

 abundant spiral tracheae running into their very ends, which 

 curve directly into the wood area of the host. 



That the chlorophyll is very active is shown by the super- 

 abundance of starch in the cells wherever chlorophyll exists. 



The hard bast is a good source of support to a plant whose 

 stems reach several meters in length, and which, owing to 

 its trailing habit and mode of twisting into ropes, must 

 often have considerable weight to support. 



