213 
plants that were observed at Brussels and at Poulkova, which is 12 
miles south of St. Petersburg: 
Date eer Sane Pare Brussels. | SnarEauar sf | 
Group | = = 
of P 1 | Squares T | Baa | 
plants. p.. 7 oul- | Temper-} of tem- emper-| of tem- | 
Brussels. jova. ature. | pera- | ature. pera- | 
ture. | | ture. | 
Days. IDES |\\ SCL SK. Os ae Cem 
ieee pe Sa jae | ee | 0 a 
2-5) 98:9 | 1490 || \ 847 1,751 || 300 | 2,394 | 
Pee) © 1929 161.4 || 550 3,730 || 458 4,411 
| hee 138.0 | 169.5 17 6,497 BYE) 6, 100 
ae | 160.4 | 184.2 || 1,102 | 11,506 | 807 9,77 
Gree 181.6 | 190.5 || 1,471 | 17,764 || 912 | 11,527 
Tin a 222.0 | 223.0 || 2,219 | 31,615 } 1,460 | 20,700 
| | if 
In taking these sums, which all relate to positive temperatures on 
the centigrade thermometer only, Linsser begins with April 8 at 
Poulkova, because on that date the gradually rising daily tempera- 
tures pass through the freezing point. It would have made no 
difference if he had begun with January 1, or December 1, or with 
the date of lowest mean temperature, which would be about the 
middle of January. On the other hand, for Brussels his sums begin 
with January 15, which is the date at which the lowest mean daily 
temperature occurs, which temperature is about +2.5° C., so that 
if he had begun with January 1 there would have been a constant 
sheht addition to all the numbers in that column. The dates of 
blossoming are given in days counting consecutively from the Ist of 
January, and may be converted into the days of the month or vice 
versa by the following table: 
Day of the | _| Day of the 
year. . | year. 
Date. aa Date. | = ae a 
: ead Leap. | — Leap 
Javelin jl 2 eae = = eee 1 PATIO US pil aes mee) 4c eee ee 213 | 214 
eI GURIsygle ee ee ose oe | 32 32 September fe ee ee ee B45 
Marchi 22 eg EB Te Ae 60 | 6 F October lke2 22 225 eee 274 275 
eine goes ew eS Ot |) = “92: "November 1 ©--- 72. "2 = 2k 305 | 306 
ILD ap 4, 2p ee Ale re 121 122 | Mecember le = ee eee 335 336 
AUIS pe noes 2 oye ae ee ge ae 152) 158 | Jandaryeles eee ee ee eae ee | 866 367 
raliysleten were ihe AER 182| 183 | | 
| | 
If we take the difference between the sums of the temperatures for 
the first and seventh groups of plants in the preceding tabie we obtain 
for Brussels 1,972° C., and for Poulkova 1,280° C., or a difference of 
about 700° C., which corresponds to about forty days at Poulkova, so 
that we must immediately conclude that the same stages of develop- 
