i62 American Horlicultural Society. 



normal turgidity, and every life function ceases. In the ripening process 

 water is expelled, but in a very ditterent way from evaporation by heat. 

 Desiccation by external means does not ripen the tissues. The latter may be 

 prevented, by withholding water, even more readily than induced, unless 

 careful attention is paid to the condition of the plmt at the beginning. The 

 point here is, that this large amount of water in living plants —amounting to 

 four -fifths their weight — is essential to them ; necessary to their continued 

 existence, and to their normal development. 



But this is not all. About one-half the weight of the dried substance of 

 plants is water in another form. It is not really water as it exists, but the 

 elements of water, and these, along with carbon, make up the solid substance 

 of the plant. The water elements are oxygen and hydrogen, one part, of the 

 former to two of the latter by bulk, or, by weight, of eight to one ; and these 

 proportions remain the same in the composition of wood, or rather of the 

 substance called cellulose, of which wood mainly consists. When plant-tis- 

 sues have been thoroughly dried in an oven kept at 212° Fahr., one might 

 suppose that there could be given otf no more water from the hard, perhaps 

 brittle, substances. But if these are now burned, the most of the material 

 passes off, as we know, as gases. If the combustion is imperfect, there is 

 more or less visible smoke ; but if the material is completely oxydized at 

 first, nothing escapes which can be detected by the eye. Now nearly one-half 

 these invisible products of the burning, kiln-dried wood is the vapor of water, 

 which has only to be cooled to reach the liquid state. In the process of com- 

 bustion, the water elements are united again with each other, but the com- 

 binations in which they were held in the wood are broken up. 



It thus appears that the abundant substance which we know in nature as a 

 typical liquid, the type of instability, the most impracticable thing possible 

 one might think in building solid structures really does constitute something 

 like nine-tenths, in one form or another, of the frame-work of plants. If so) 

 surely the first place should be given it in a discussion of plant nutrition. 

 Water is used in abundance as a necessary part of the plant tissues, in a me- 

 ■chanical sense, and it is used as a true food substance, constituting in a chem- 

 ical sense a considerable portion of the solid material of the plant structure. 

 In the former it remains water ; in the latter condition it is no longer a 

 liquid, but joining in a molecular sisterhood with carbon forms the wood 

 substance of plants. 



Experiments have conclusively proved that plants obtain the water which 

 they require, for one or both the purposes just mentioned, through the roots 

 and through the roots only, if we confine ourselves to our garden and field 

 ■crops. It is very often supposed that leaves absorb moisture from the air, 

 and because wilted plants revive at night when the dew settles upon them, 

 this is supposed to be proved. So when a potted plant is allowed to wilt for 

 want of water it may often be seen to regain its normal condition by sprink- 

 ling the top with water in such way as to give none to the roots. But these 

 things are entirely possible without absorption by the leaves. As the roots 



