SUMMER HEAT AMPLE 



21 



month the mean temperature of which does not fall below 662 

 degrees Fahr. As will appear presently, this temperature test 

 should not be taken alone, but it will serve as a standard to show 

 one feature of the horticultural adaptation of the California 

 climate. Boussingault claims the need of 662 degrees Fahr. for a 

 single month. To be sure to include this, the accompanying table 

 gives the average summer temperature at the leading fruit-growing 

 centers named. 



Average summer temperature at various California points 



Coast and Coast Deg. Deg. Eleva- Deg. 



Valleys F. Interior Valleys F. Foot-hills tion F. 



These points are selected because the European varieties of 

 the grape reach perfection in their vicinity. The excess of heat 

 above that required, as is found at all the interior points mentioned 

 in the table, results in a very high sugar percentage in the grapes, 

 and contributes to the ripening of a second and third crop, as 

 will be noted presently. The superior length of the growing season 

 in California, of course, is an important agency toward the same 

 end. 



DIRECT SUNLIGHT ALSO A REQUISITE 



Count de Gasparin was first to point out that not alone sufficient 

 heat, but abundance of continuous sunshine is a requisite of per- 

 fection in fruit growth and ripening, and on his authority may be 

 based a claim of exceptional value to the fruit grower in the months 

 of cloudless skies which are characteristic of the California summer. 



"The solar rays," says Gasparin, "do not only produce heat, but 

 bring us light, and the effects of the heat and light rays differ in a 

 very pronounced manner. Without light there is no fructification; 

 it is not necessary that the want -of light should be complete that 

 there should be a failure of fruits. In fact, diffused light alone does 

 not suffice for the greater number of plants; cultivated plants will 

 not ripen their seed without the direct rays of sun, and the longer 

 they are deprived of it the smaller the quantity which they will 

 mature."* 



* Cours d' Agriculture, t. II, p. 96. 



