20 College of Forestry 



may be designated as Frank's wound gum. In order to prove 

 this he made detailed studies of pophir (Fopulus halsanifia) 

 twig's, in which he aHowed unpeeled twigs to dry out in a 

 room so. that generally from one to two weeks elapsed before 

 they showed signs of dessication. lie observed that death nat- 

 urally took place first in the vicinity of the cut ends and that 

 the bark and outermost portions of wood likewise died before 

 the deeper-lying ones, M'hich were better protected from dry- 

 ing. The protoplasm became rigid and lost its fine granular 

 structure ; in addition the most of it turned a light brown. 

 In the twigs, soon after the death of the parenchyma cells, 

 there occurred a darkening of the wood and especially of the 

 bark. Miinch furthermore determined that the dark color 

 originated exclusively from the brown substance which was 

 present in the parenchyma cells and that the darkening ap- 

 peared first in the parts which were more affected by the 

 drying, that is, at the ends and at the periphery. Thence it 

 proceeded ra])idly toward the center of the twig. 



Upon making radial sections at the place where only the 

 outer part of the Avood was darkened and the inner was still 

 white, Miinch observed that the ])ith ray cells at the boundary 

 between these two areas contained several brown globules. He 

 found that all the cells, even the inner ones which were still 

 uncolored, had died and did not respond to the plasmolysis 

 test. Farther toward the outside scattered brown droplets 

 were noticed in the vacuoles of the protoplasm. In the cells 

 situated near the periphery of the twig these brown droplets 

 had coalesced to form larger drops. These frequently con- 

 tained several small bubbles. Miinch states that examina- 

 tion of such cells showed nnmistakably that the liquid con- 

 tents of the vacuoles suddenly becoine changed at some time 

 after the death of the cells to brown viscid drops which became 

 finn and hard after coalescing. In wood that was still fur- 

 ther dried he observed cracks in some of the individual brown 

 globules. 



