239 
trees and examining them very frequently Hoffmann seeks to deter- 
mine how accurately the date of the beginning of vegetation or the 
flow of sap can be determined by the swelling of the buds and the 
visible cracking of the delicate pencil lines of paint. He finds that 
the date can be determined to within one day when spring comes on 
rapidly, but within eight days when it comes very slowly. The cor- 
responding uncertainty or variability of the sums of the maximum 
sunshine thermometer from the swelling of the buds up to the date 
of the first blossom, for instance, for Castanea vulgaris, is 4 per cent 
while the uncertainty of similar sums, counting from January 1, 
is only 1 per cent. These and similar data are only deducible from 
observations made upon the same tree or bush from year to year; 
the variations are materially increased when different plants in dif- 
ferent localities are observed; moreover, they are based upon observa- 
tions for only four years, which period is not long enough to give a 
reliable value of the relative uncertainties. As in previous cases 1n 
making up these abstracts, I give Hoffmann’s actual figures in the 
following summary, which I have compiled by collating the few 
observations published by him in the Zeitschrift during the years 
1870-1890. I have selected only the few plants for which he has 
published the sums for several years or for two localities, so that 
comparisons may be made and a judgment arrived at as to the pro- 
priety of his method. It will be observed that Hoffmann has, when 
possible, observed the same tree or bush from year to year, so that 
the problem of the influence of heat is much more definite than when 
different plants or a general mass of plants is observed; but, on the 
other hand, single plants are more lable to irregularities produced 
by special disturbances which would exert no appreciable influence 
on the average of a large number of similar plants. 
Temperature sums at Giessen (Hoffmann’s method) from the first swelling of 
the buds to the first blossom. 
[Z. O. G. M., Vol. XVII, 1882, p. 127. All in Réaumur degrees. ] 
Plant. 1866. | 1867. | 1868. | 1869. 
Castanea catigmmessee oan ses Me eee ae Len, Leh ee AA EAD eae cee ees 2,044 | 2,142) 2,085 2,317 
Gatalparsyvain caroline secs es aan teen c ens nae RE aS Re Ss 2,149 | 1,984 2,547 
Lonicera alpigena: | 
ins ti SMeCiMNe nis sims meee er ieee 2M ae Se Tee 891 1,058 1,014 
SCCOnG SPCCIIN ON yaaa aaa ae se os 2 Re ees e5t vecceesi[sses—ese 919} 1,058 1, 032 
Persica vulgaris: 
IESi SpeCimMenii se see es eee eowee aes sed So cee sous ee ese 659 678 774 788 
Secondsspecim Cn aesse aa ae seen eee eee Seah cone eee 893 670 O84 eee sees 
Syringa vulgaris: 
St SPECUIMON Hs sae 5. > hie eee e eee Seren ooo oS Vanes same sone 1S S88h|Peeeeeo- 1,315 1,248 
SECONd SPECIMEN shat 5 Se Seer Ne aE ae es Leese Sse! TOO res aces 1,181 1,166 
Vitis vinifera: y 
HPStispecimenee asda a 5 eR mye ee oes ee ee kee ees beple ss Sarg a 1,040 1,531 
SeOcondrspecimicnrysses 4 os rere ee ee ob ee cee sec teesccec |b saseas8 856 1, 222 
