15 



arc the heaviest, therefore uniform blocks may be cut from each 

 leaf and weighed on a delicate balance, and the diflEerence in weight 

 noted. 



In many houses running north and south the crops on the east 

 side receive the benefit of the m.orning light, and those on the west, 

 the afternoon light, and from data gathered from practical growers 

 we find a difference in yield of 15 to 30 percent, in favor of the east 

 side plants. Even greater differences will be found by comparing 

 the middle rows in cucumber houses with either of the outside rows, 

 whether with an eastern or western exposure. The inside rows 

 are often so shaded and the yield so small that it is a question 

 whether it is worth while to grow them. 



The east radii of trees growing in the open show a greater 

 growth than the west radii. In making observations of this 

 nature it is of course necessary to select trees not shaded by other 

 trees or by buildings, if reliable results are to be had. 



A long row of ash trees, planted in 1882 an equal distance apart 

 on a road running north and south, was examined very carefully a 

 few years ago, an opportunity offering when it became necessary 

 to sacrifice ever>^ other tree. The north, east, south and west 

 radii were carefully measured and the growth foimd to be 24 per- 

 cent, greater on the east than the west side of the tree. This high 

 percentage may be explained by the fact that the roots were more 

 favorably located for growth on the east than the west side, where 

 some had been amputated. Practically all of the substances 

 which make up the bulk of the tree are obtained from the foliage 

 through the process of photosynthesis, and if the light is better 

 on the east side of the tree than on the west, carbon assimilation 

 will be more active and more plastic substances, used in growth, 

 will be found there. 



A large number of measurements of forest trees, some of which 

 were 200 years old, showed that the east radii were about 17 per- 

 cent, larger than those on the west side. Most of the measure- 

 ments were taken from stumps cut from 2 to 5 feet above the 

 ground, and the unequal growth often formed by large roots near 

 the surface was not present. Trees growing on the eastern slopes 

 of mountains show an unusual development of the east radii, while 

 those on the western slopes show the greatest growth on the wes«t 

 side, as might be expected. The records obtained from tree 

 measurements undoubtedly represent quite fair averages of morn- 

 ing and afternoon light, as many seasons' growth is included. 



We have, therefore, more than one way of determining the 

 difference between morning and afternoon light, any one of which 

 is capable of giving fair results. 



It will be observed that the results obtained from the chemical 

 method differ somewhat from those obtained from the measure- 

 ments of trees; but in the former case the data are for only one 



