173 



(3) RIPENING. 



During increasing heat : ' " C. 



Fruit of the elm tree 12.0 



Green peas 14. 2 



First cherries; hroad beans 16.0 



First mowing of sainfoin 17.0 



Currants; raspberries; strawberries; cherries 17.8 



Morella cherry tree; apricot; plum tree; barley; oilts 18.0 



Rye 19. 



Peach tree: harvest of corn 20.0 



First figs ; green gage plums 21.0 



First grapes, called madeleine ; melons in free earth 22.5 



Hemp . 22. 6 



During decreasing heat (for fruits which have received a sufficient quan- 

 tity of increasing heat) : 



Horse-chestnut 18. 2 



Indian corn; potatoes 17.0 



Walnuts and chestnuts 16.2 



Pomegranates 15.0 



Saffron 13.0 



Olives 10. 



Note. — It can be easily understood that the fruits which require the greatest 



I.rolongatiou of heat ripen last and are gathered at periods of the lowest 



temperatures. 



Lachmann, in his Entwickelung der Vegetation, counts the sum 

 total of all the temperatures at his station (Braunschweig, Germany) 

 from February 21 onward. 



Linsser, for north temperate countries, counts from the date when 

 the temperature 0° C. is attained, but for warmer countries he counts 

 from the date when the lowest temperature of the year is attained; 

 which date would, according to his calculations, be the 8th of Febru- 

 ary at Braunschweig instead of the 21st of February; but, according 

 to the normal values resulting from the thirty years of observation 

 by I^achmann. this change would only make his sum totals about 

 10° C. larger. 



Tomaschek, as quoted by Fritsch (18G6, LXIII, p. 297), takes the 

 mean of all positive temperatures as observed at () a. m., 2 p. m., and 

 10 p. m., omitting the individual negative observations instead of the 

 negative daily averages. He counts the sums from January 1 ; this 

 method gives figures that agree very closely, at least in Europe, with 

 those given by Fritsch's method. 



Kabsch, as .quoted by Fritsch, attempted an improvement on the 

 method of Boussingault. His fornnda is especially appropriate to 

 the annuals, but not to the perennial plants. His method of comput- 

 ing the thermal constant is exi)ressed by Fritsch in the following 

 formula : 



my- 



