[ADAMS] CLIMATIC FACTORS IN RELATION TO PLANT LIFE 113 
TABLE II. 
MAXIMUM AND MINIMUM TEMPERATURES (F) 1909-12. 
Maximum. Minimum. 
Dawson ace sinc ark ME ar 82 to 86-5 —54 to —62 
WiCtOniamari se ae 0 ale cae APE 86-7 to 89-8 14-2 to 19 
Barker Ville RER AN eso sac eres creer 75 to 82 —25 to —40 
PMONTONE wy: cise ee eee 87 to 94 —39 to —52 
OucAppelles eases aise ate pete he 88-5 to 95 —38 to —47 
WINTLIDERS Set ee ak ere de es 89-2 to 99-2 —36:2 to —42 
ROG AT hae Sie ee ie EE 86 to 97 —27 to —36 
EOKOMUO ME Ae ei eee ee nn 92-7 to 103-2 — 6-8to —11-7 
Montre EE EE Eee ee ail eis tts 86-5 to 94.5 —16 to —19 
Sole M EE PE 77-5 to 81-5 — 7-7to —14 
Al a Re tate Re ees soe he 86-3 to 98-7 — 1-4to —11-6 
Soom O MES eet en. ee Mere darts 82 to 86 — 2 to —10 
Active growth is considered to begin when the mean temperature 
reaches 41° F. or more, subject to certain qualifications. The com- 
mencement of spring in the popular sense may be considered to be 
coincident with the beginning of the period of active growth. Phenol- 
ogists are wont to fix this date by observations made on the stage 
of growth reached by certain plants or by phenomena relating to the 
animal kingdom. But it can be determined equally accurately from 
observations on temperature based on the five-day period mentioned 
above. It sometimes happens that the mean temperature 
of a five-day period is above 41° F. during which period 
some growth is made: then a five-day period follows with a mean 
temperature below 41° F. with a corresponding check to growth. 
The period of active growth is taken as beginning on the first day of 
the five-day period with a mean temperature of 41° F. or more which 
is followed continuously by other five-day periods each having a 
mean temperature of 41° or over. This date appears to agree well 
with actual observations of the stage of growth reached by plants 
at the time in question. Thus at Ottawa in 1915 the date of beginning 
of active growth as measured by temperatures was 6th April and on 
the 7th of April, hellebore and snowflake were in flower; iris, arabis, 
doronicum, oriental poppy and clover were growing steadily and 
bees were gathering honey. In 1916 at Ottawa the date as deduced 
from temperatures was 11th of April. On the 10th of April the first 
flowers of hellebore were seen, tulips and snowflake were making 
considerable growth and bees were flying. Snowflake was in full 
flower on the 15th and iris was growing steadily. 
It seems to be desirable to use some such term as “active growth”? 
or ‘continuous growth”’ in the sense defined above in contradistinction 
“Sec. IV, Sig. 2 
