mSTORY OP HORTICULTURE IN MINNESOTA. 205 



ficient to ripen tlie fruit of an}' i^iven kind, thiit there are varieties of trees of 

 such fruit, or new varieties may be originated, which will withstand the win- 

 ters and seasonal extremes of temperature in such climate. 



The fruits named have been carried bj' civilized man in his migrations from 

 milder climates northward. The change in the constitution of the tree has 

 been gradual. Naturalization from mild to nmch colder regions has been ac- 

 complished by the production of new varieties, the essential characteristics 

 of which have been earlier ripening of the fruit, and greater hardiness of the 

 tree to enable it to endure severer cold oi- greater ditterences of seasonal 

 temperatures. 



It is a mistake to suppose that trees adapted to a southern climate and re- 

 quiring a long growing season, can ever be acclimated to one much shorter. 



As a general rule applicable to our continent, every additional degree north- 

 ward shortens the growing season aljout four days. Our season at St. Paul 

 is therefore twenty days shorter than that of Philadelphia. 



Varieties of fruit which ripen at Philadelphia must fail here in consetiuence 

 of our shorter growing season. 



But length of growing season is not the only condition — every -variety of 

 vegetation requires for its maturity of leaf or fruit a certain sum of heat. 

 Wheat, for example, requires, according to the observations of Boussingault, 

 from 2,000 to 2,200 degrees of heat, centigrade, which, with a mean temper- 

 ature of 20 degrees centigrade, would require from 100 to 110 days to ripen. 



Every variety of fruit requires for ripening, a certain sum of heat, but in 

 ascertaining the requisite quantity for plants growing exposed to the sun, the 

 thermometer consulted should also be exposed to its rays. This is the ap- 

 proved method of observation, which, when applied in our climate, will, I 

 think, give results highly tavorable — showing that the solar heat of our grow- 

 ing season is sufflcient to mature all early varieties, not only of the fruits 

 named, but of peaches, also. 



Our mean Summer temperature is greater than that of Paris, in the vicinity 

 of which all the fruits named are cultivated with great success. The obstacle 

 to our success in fruit growing, thus far, is our Russian winter climate. 



The fruits I have named are cultivated with success in Russia. Pallas, who 

 visited Moscow, near the close of the last century, states that these fruits 

 were then cultivated in that vicinity, "and sold at reasonable prices." 



Mentelle & Maltebrun, in their great work published in Paris, in 1803, give 

 an account of the fruits cultivated in Russia, embracing apples, pears, cher- 

 ries and plums. A variety of apples, grown at Kervsk, they describe as 

 weighing four pounds, of a delicious flavor, and keeping a long time. Another 

 variety of apples grown in the vicinity of Moscow, which was brought from 

 China, they describe as so transparent that when held up to the light, one 

 can count the seeds in it. They state that in several of the districts of Russia, 

 the exportation of fruits, and especially of apples, is an extensive branch of 

 commerce — that the exportation of apples from the towns of Kalouga and 

 Simbrisk, amount to from 18,000 to 20,000 roubles annually ; and that in some 

 parts of Russia, the cultivation of the cherry for the manufacture of Kirsch- 

 wasser, is carried on very extensively. 



