498 



BOTANICAL GAZETTE 



[JUNE 



There are several possible explanations of this localization on 

 the younger portions. The epidermal membranes are not so well 

 developed in the young leaves and it is easier for the cyanide to 

 enter. The younger and more rapidly growing portions of a plant 

 are the first to suffer in absence of oxygen. It may be that the very 

 reactive state of the protoplasm in these parts makes them less 

 resistant. 



Fig. 2.— Older plants, in which there is a steady change in the location of the 

 injured areas, until with old bearing plants the killed area is basal, and is not limited 

 to the margin of the leaf. 



The rapidity with which cyanide can kill the plant tissue is 

 another point of interest. The plant can live in the total absence of 

 atmospheric oxygen for some time. However, 5 hours after the 

 beginning of a damaging fumigation it was possible to see the dead 

 leaf areas, dark and water-soaked in appearance. 



It may be said that there are several things which stand out 

 prominently as causes for the unsatisfactory results often secured 

 from greenhouse fumigation with cyanide. First, there is a lack of 



