THE PLANT WORLD 105 



of an acre and one-third of an acre. Aside from the value of this esti- 

 mate, it will be seen that, inasmuch as the amount of sugar obtained 

 from a tree during a sugaring season depends upon the activity of the 

 leaves during the previous growing season , that there will be considerable 

 difference due to this variation in amount of leaf surface. This in turn 

 will depend on the various conditions which prevail during the growing 

 season, as e. g. the inroads of insects or the amount of sunshine. 



2. It was also calculated that during twelve days, during the unfold- 

 ing of the leaves, 481.6 pounds of water previously found in the stem 

 were lost by transpiration. This does not include water ab.sorbed from 

 the soil. 



3. The pressure of sap is largely independent of gas pressures, and 

 indeed much greater than can be explained by the amoinit of pressure 

 exerted by the expanding gases in the stem under the influence of the 

 rises in temperature actually found. It would appear that the pressure 

 found is due to the activities of the living cells of the sapwood, and is, 

 in part at any rate, an osmotic phenomenon. The root pressure has no 

 bearing on the pressure in the trunk. 



4. The significance of the accumulation of water in large amounts 

 in the stem is to be found in the necessity of having a ready and abund- 

 ant supply during leaf expansion. 



5. From a good tree the yield of sap varies from nothing on a poor 

 day to 8,300 grams, containing 354 grams of sugar, on a good day. 



This excellent study, from which we have gleaned for our readers 

 but a few of the many valuable data, deserves wide and careful study. 

 Teachers will find it a very instructive essay, and it is to be hoped that 

 the edition is large enough for a very wide distribution. 



The Fourth Annual Report of The Home Gardening Association of 

 Cleveland, Ohio, has recently been received. This association has cer- 

 tainly done a splendid work. It has "pointed out a way to make the 

 city wilderness to bloom, to cause flowers to blossom in the smallest 

 places." Its object has been accomplished by the distribution of seeds 

 and bulbs, by the delivery of lectures in schools on gardening and its 

 results, by the holding of flower shows, and by the offering of prizes. It 

 is planned to extend its influence and aid during the coming season to 

 the establishment of school gardens. Teachers will find in the report of 

 twenty-six pages many valuable suggestions and some useful information 

 in regard to gardening as an educational factor. 



" Tree Studies " is the title of two series of photogravures, " Trees 

 and Their Barks " and "Leaves, Flowers, Fruits and Buds," which will 

 be published by Romeyn B. Hough. Judging from the examples we 

 have seen, we may say without reserve that nature-study teachers will 



