42 



TRANSLOCATION IN PLANTS 



of the xylem. Although some of the shoots were sHghtly 

 wilted, there seemed to be no permanent ill effects. It is 

 to be regretted that only stems having a latex system were 

 tested by scraping the cambium, for it is possible that the 

 latex system plays some role in transport. Hanstein 

 (1864), Schimper (1885), Kniep (1905), and Simon (1917) 

 give fairly strong evidence, however, that the latex system 

 is not effective in food transport. In all the other experi- 



Table 8. — Influence of Scraping the Cambium upon Transport When 



THE Xylem Is Removed 



Measurements in millimeters of increased growth. Rhus. P = phloem cut, 



cambium not scraped. A' = xylem cut, cambium surface thoroughly 



scraped 



* Possibly misread. Omitted in averages. 



ments the behavior of Rhus was not different from that of 

 several other plants having no latex system, so it is likely 

 that the undifferentiated cambium is ineffective in rapid 

 transport for appreciable distances. That the cambium or 

 similar meristematic cells may take some part in trans- 

 location over short distances, however, seems not impos- 

 sible. Active streaming which should favor transport in 

 such cells has been observed by Velten (1872) and Bailey 

 (1930). The only certain way of determining whether the 

 cambium and immature cells developing from it are effec- 

 tive would be to cut all the mature phloem. 



