402 MISSOURI STATE HORTICULTURAL SOCIETY. 



more heat does a given area of land receive in a summer's day from 

 the sun. 



This is because the summer day lasts twelve hours at the equator^, 

 and longer and longer as we go north, until arriving at very high lati- 

 tudes there is no sunset. Why, then, the colder northern climate? 

 Because the winter day is as short as the summer day is long; and 

 through the winter vast masses of snow and ice accumulate and chill 

 the whole year. Yet the fact remains, that an acre of wheat receives- 

 more of direct sunlight in a summer's day in Ohio than in Mexico, and 

 more in Canada than in Ohio. It is also known that wheat matures in 

 fewer days in Canada than in Ohio, and in Ohio than in Mexico. This 

 shows the influence of sunlight in ripening grain and fruits. 



Xenos Clark. 



why are some trees hardy? 



In a note appended to Mr. Tuttle's criticisms of Professor Budd 

 (^Prairie Farmer.^ Jan. 2,) we stated, in effect, that the smaller the 

 water-carrying pores or cavities in the wood of a tree or shrub, the less 

 would be the expansion and contraction at any one point, or at all 

 points, by freezing and thawing, and that other things being equal, it 

 would seem that the finest grained wood should be the hardiest in a 

 changeable climate. A particle of water one-hundredth of an inch in 

 diameter expands one nine-hundredth part of an inch in freezing*. 

 and the elasticity of the fibres may be supposed to stand that strain. 

 But a water cell one-tenth of an inch tjirough would, in freezing, ex- 

 pand one-ninetieth of an inch, and this might rend and disorganize the 

 structure enough to kill the life of tjie tree or shrub. Mr. Tuttle gives 

 some illustrations of fine and coarse grained structures, which appar- 

 ently militate against this explanation. His statement that hardiness 

 is an inhericed quality does not at all explain the secret or cause of the 

 hardiness. The graft or .progeny is merely a continuation of the pa- 

 rental tree structure. 



Mr. Vincent's theory brings in a factor that may explain it. Water 

 is one of the exceptions to the general rule that heat expands and cold 

 contracts. Nearly all solids continue to contract by cold and to ex- 

 pand by heat. Water contracts by cooling, down to about 09°, but 

 expands on further cooling, so that in simply sinking from 39° to 32°, 

 it expands over one-ninth of its bulk. Now, as we understand it, Mr.- 

 Vincent explains that in the hardier woods the pores are filled with 

 starch particles instead of water, and starch being a solid substance^ 

 expands and contracts but little with the changing temperature. This 

 is theoretically borne out by the fact that fully ripened woods, that is> 



