YALE AGRICULTURAL LECTURES. 37 



and otheraquatic silici cms plants grow, the addition of lime, 

 which removes the excess of silica from the soil, favors the 

 growth of less silicious plants. The silica then on corn-stalks, 

 cereal crops, bamboo, rattan, and such-like, he deems an ex 

 cretion. The " lodging " of crops he thinks may be owing to 

 a weakness of cellular tissue, which may arise from a lack of 

 some nutritive matter or another, or from excessive transpira 

 tion of water. It is known that a plant sucks, sponge-fashion, 

 its juices from the soil, through the extremities of its roots and 

 rootlets. In this water all sorts of mineral matter are dissolved, 

 and with them a certain proportion of carbonic acid and am 

 monia ; well, the plant has a very wonderful power of selecting 

 from this soil-moisture just as much mineral matter as it needs 

 for its growth, and of rejecting all the surplus. Water, how 

 ever, oozes in, by the principle of endosmose, and is sucked up 

 ward from cell surface to cell surface, until it gets to the leaves, 

 where the blowing of wind and the shining of sun upon the 

 leaf surfaces evaporate the water through the little pores, 

 stomata, which communicate with the outside air. The plant 

 wants only just so much juice passing through it at once, and 

 if an excess is poured through throughout a warm, damp sea 

 son, you see how likely it is that its constitution should be 

 weakened. Recent German experiments which have come to 

 Professor Johnson's observation suggest that the beneficial 

 effects of salt, plaster of Paris, and other mineral fertilizers, are 

 due to their preventing this excessive transpiration, or rushing 

 of an excess of water through the plant. Mr. John Johnston 

 sows five bushels of salt on his wheat-fields, " to give stiffness 

 to the straw and prevent rust." The old farmer observed the 

 effect; our chemical friends think they have discovered the 

 cause. 



Moreover, what Professor Mapes will scout as sheer heresy, 

 Johnson says that the mineral phosphate from Estramadura 

 and elsewhere is as good for fertilizing crops, if it be prop 

 erly divided mechanically, as bone phosphate thus directly 



