194 



leaves with smaller intercellular spaces ; this may be found in plants near 

 salt springs and on the sea shore. 



Among our cultivated plants, tobacco suffers most ; it reacts exactly 

 as in hot, dry summers and forms fleshier leaves with a reduced burning 

 quality. Hunger^ confers these observations, made in Europe, and says 

 of the cultivation of the Dehli-tobacco on Sumatra, that the leaf most 

 valued, most grown and most carefully selected, is large, thin, poor in oils, 

 and develops only in the presence of abundant water as in continued rainy 

 weather, while in dr}^ weather small, thick, less valuable leaves, covered with 

 many glandular hairs, are formed. 



The Improvement of Soils Which Are Becoming Compact. 



The improvement of the easily packed clay soils will have to lie in the 

 increase of their ability to be worked. Heavy soils are unyielding, i. e., they 

 offer great difficulty by sticking to the farm implements, when damp, and by 

 hardness, when dry. Great clods are produced which generally do not fall 

 apart easily if the clay or red clay soil is poor in humus. It is well-known 

 that the best plan for working soil for spring planting is to break it up in 

 the fall and let it lie in rough furrows. The freezing of tlie water in the 

 interstices during the winter months reduces the tough clods to a mellow 

 crumbling mass. 



These advantages are availalilc only tor spring i)lanting and disappear 

 after the heavy rain storms of the summer. Therefore care must be taken to 

 prevent caking by supplying humus or marshy earth ; fertilizing with long 

 strawy manure is very greatly used. However, Uming and marling the soil 

 have given very efifective results. Practical experience has shown that the 

 addition of calcium, which is in solution in the soil as the bi-carlionate, will 

 hinder its caking. 



A definite amount of all salts, even of tlie most effective, calcium and 

 magnesium, must be kept in solution in excess of the amount necessary to 

 start action if any deposition of the clay particles is to take place. Even in 

 rivers the flocculent action of dissolved salts makes itself felt since, for 

 example, the sediment in rivers flowing from lime regions is more quickly 

 deposited than in those from regions poor in lime-. For agriculture, fria- 

 bility becomes directly important since upon this depends the proper state of 

 tillage. The small bits of the soil behave similarly to the clay flakes. Hil- 

 gard proved the action of lime by tempering solid clay soils with i per cent, 

 quicklime. While the original clay soil became as hard as stone after drying, 

 that mixed with lime was found to be crumbly and mellow. Since, besides 

 a continuous mechanical working of the soil, the salts also condition its 

 looseness, this must be the case, to an equal extent, in forest soil also. If 

 the soluble salts, determining the friable structure, are decreased, as by 

 excessive use of litter, covering with raw humus, the leaching of the upper 

 layers, etc., a packing of the soil must take place. 



1 Hungrer, F. W. T., Untersuchungen und Betrachtungen iiber die Mosaikkrank- 

 heit der Tabakpflanze. Zeitschr. f. Pflanzenkrankh, 1905, Part V. 

 - Ramann loc. cit. p. 226. 



