Discussio7i on Vegetable Physiology. 37 



tree. I do not agree with the professor's theory that the sap does 

 not descend. The process of downward flow is caused by endosmos 

 and exosmos of the fluids. 



3fr. (t/66s, of Minnesota — The protuberance caused by girdling 

 a branch with a wire or ring is proof of the downward flow of sap. 



3Ir. Pierce, of Minnesota — Our trees in Minnesota often die from 

 starvation, when we think they are winter-killed. They fail to 

 ripen their wood properly in the fall and starve out during our long, 

 dry winters. They wall withstand our winters if they are well 

 supplied with starch, not otherwise. 



Prof. Popenoe, of Kansas — Vegetation, to a certain extent, con- 

 tinues through the winter. Mr. Munson is doubtless correct in his 

 views on this subject. 



Prof. Robson — It is impossible for the people of the Western and 

 Northwestern States to grow the Belgian pears. This has been 

 tried to the great disappointment of many of our older horticultur- 

 ists. This is owing to physiological conditions. We have not 

 studied these subjects as we should have done, or we would not con- 

 tinue to try to grow these varieties that are not adapted to our pe- 

 culiar climate. I have sometimes thought the live-stock men were 

 ahead of us fruit-growers in this, that they are more fully educated 

 in animal physiology. They understand pretty fully the laws 

 of stock breeding; we very poorly the laws of cross fertilization, 

 hybridization, etc., in the plant world. We must learn to produce 

 varieties adapted to our soil and climate, and depend less upon 

 chance to supply our demands. 



3Ir. Munson — Dr. Gray has told us many valuable things in re- 

 gard to plant growth. We can not successfully combat his views 

 on these subjects. I can not fully indorse the essayist'.^ views in 

 reference to the flow of sap. The facts are, the sap goes where it is 

 wanted in the economy of the plant ; let this be downward, up- 

 ward, or even to one side, as the case may be. I think the j)ro- 

 fessor is probably mistaken in regard to there being no visible in- 

 terruption of growth, at the point where the branch entered the 

 house. It is very injurious to trees to have their foliage stripped 

 off", as we nurserymen sometimes do, in hurrying up our fall dig- 

 ging, before the season of growth closes. 



