34 



red clover, from different localities, were examined during 

 the winter, and the same effects were always visible. 



A number of plants were taken up and placed in a stove in 

 their native soil, having a temperature of 60° to 65°. Of 

 those taken up in November, about one-half of them con- 

 tinued to live, while of those taken up in January all died ; 

 some of the latter had their soil changed, but they also died 

 away in about ten days. Of those plants which were taken 

 up early in the season, some of them survived, because their 

 gap vessels were not irremediably damaged ; while in those 

 taken up later, the vessels were destroyed to an extent incom- 

 patible with the life of the plant. 



It being proved, then, that the clover crops are destroyed 

 in this country by the frost, the next inquiry is— Why are 

 they injured on particular soils, or sometimes on a soil where 

 this crop has been successively grown, — as every third or 

 every fourth year? Upon certain soils of the New Red 

 Sandstone at Fishlake Fenwick, red clover has been grown 

 every third year for a series of years (this is shown in the 

 Yorkshire Agric, Report^ page 125); while upon portions of 

 the Chalk Wolds of Yorkshire, neither red clover nor white 

 clover can now be scarcely cultivated at all ; and it may be 

 safely asserted that it is only upon the more pulverulent soils 

 of the Magnesian Limestone, of the Chalk and of the Sand- 

 stones of the Coal Measures, and some of the lighter soils of 

 the New Red Sandstone and Oolite, that this crop is injured 

 by the frost. If it is destroyed on a stiff soil, it is from an 

 excess of water and because it is too wet; the natural habitat 

 of red clover being a dry compact loam, firm and close 

 on the surface. 



The true answer to this inquiry is, that the cause of injury 

 by the frost is owing to the want of a certain degree of 

 cohesiveness of the particles of the soil among themselves ^ 

 and hence the soil's power of retaining heat is diminished ; 



