241 



Many of the plants observed by Hoffmann show such discordant 

 sums from year to year as to prove that his method has no meaning 

 for them, but for others the agreement is such that he reconnnends 

 them to be observed in connection with the observations of the sun- 

 shine thermometer, as follows: 



For the following plants observe the temperature sums from tlic 

 first swelling of the buds to the first flower blossom : Castanea vesca, 

 Bupleurum falcatum^ GovydaliH fahacea^ Dianthus cartiivsiano- 

 rum^ Lonicera alpigena^ Salix dafhanoides^ Syringa vulgaris, Amyg- 

 dalus 7ia7ia, Alniis incana, Alnus viridis, Atrova belladonna, Betula 

 alha, Crataegus oxyacantha, Larix europaea (up to the date when 

 the pollen first falls froni the anthers), Ligustrum vidgare, Lonicera 

 tatarica, Prenanthes purpurea^ Prunus pad/us, Pninvs spinosa, Rham- 

 nus fraiigida, Rihes aureiim, Rosa arvensis, Rosa alphia, Salix caprea, 

 male (for the catkin, or the flowers of the willow, the beginning of 

 pollination, as ascertained bv a light stroke on the flower, is to be 

 considered as the date of the first blossom). 



Hoffmann also applies his summation of sunshine maxima tempera- 

 tures to the interval from January 1 to the ripening of the fruits 

 and shows an excellent agreement between the numbers for 1880 and 

 those for 1881 at Giessen. 



In the Zeitschrift for 1884 Hoffmann gives his results for 1882, 

 1883, and 1884 as collected in the preceding table and says that the 

 vexed question of the thermal constant for vegetation is still far 

 from being settled ; either temperature and vegetation are independ- 

 ent of each other, which no one can easily believe, or they stand to 

 each other in a relation for which the correct expression is still 

 unknown. Pfeffer in his Pflanzen Physiologic (Vol. II, p. 114) has 

 stated that the approximate uniformity of the sums of temperature, 

 from year to year, can onh^ mean that, in general, for each year the 

 heat received from the sun amounts to about the same sum total for 

 the same date annually; but this is not in strict accordance with 

 facts, for if it were true a small change in the date should make a 

 small change in the sums, which is not always the case. Thus, if 

 for Linosyris vidgaris the dates of blossoming are August 15, 18, or 

 20, the sums from January 1 for different years will be as follows : 



From these figures we see that the sums vary from year to year 

 quite independently of the change of date. 



The thermometer Bj, similar to B,, having been sent to Upsala for 

 observations at that place, it gave from January 1 to the first blossom 



2667—05 M 16 



