The Microscope. 183 



When cool enough not to endanger the objective it is again slip- 

 ped beneath the one inch or higher power. 



This is a revelation. The microscopic balls of snow have dis- 

 appeared and in their place are as man}' little drops of liquid as 

 yet unmiscible with the glycerine, and most astonishing of all, 

 each drop of liquid is clinging to the edge of a stoma or breath- 

 ing pore of the leaf. Can it be that the little balls that compose 

 those silvery lines are each adherent to a breathing pore? With 

 rather feverish haste under the excitement of a possible discov- 

 ery, the microscopist makes another section, and treats it to a 

 hot bath more prolonged than was the first. Now the waxy ac- 

 cumulations and the liquid from their melting have entirely dis- 

 appeared, and the stomata stand out clear, clean and sharply 

 defined. 



It seems that each stoma has been heaped above the brim 

 with this deposit of white wax. Each breathing pore is some- 

 what depressed below the general surface of the leaf and this 

 little cavity is filled to overflowing with the waxy secretion. 

 This fact suggests other questions. If, as is undoubtedly the 

 case, the stomata are filled with the deposit, how then does the 

 air gain an entrance to the tissues of the leaf? In some in- 

 stances that are few and must be searched for, there are minute 

 channels through the wax balls that may be large enough to ad- 

 mit all the oxygen that is necessary and to allow the stomata to 

 fulfil their purposes. How that may be I do not know. I 

 only know in this connection that the breathing pores are piled 

 full of the secretion and choked with it, and that the judicious 

 application of heat to the glycerine surrounding the section re- 

 moves it, leaving the stomata as clear and distinct as they were 

 before obscure. 



But where does the secretion come from ? Is it exuded by 

 the guard cells of the stomata, or is it formed by the cells enclos- 

 ing the air chambers beneath the stomata and into which they 

 open ? If the latter, then the wax must be pressed out through 

 the opening between the guard cells to be heaped up in the lit- 

 tle balls that together form the silvery lines on the surface. 

 Here is a question for the investigating reader to answer. Trans- 

 verse sections of the leaves of the Hemlock or of other evergreen 

 trees will tell the story. The thin, irregular film on the general 

 surface of the leaf is probably secreted by the cells of the epi- 

 dermis. But this is also a question for the razor to settle. 



