8 BOTANICAL GAZETTE [JANUARY 
TABLE I 
NORMAL TEMPERATURE AT PorT ARTHUR FOR THE 20 YEARS 1888-1907 
| Jan. | Feb. | March {Apri May | June | July | Aug. | Sept.) Oct. | Nov. | Dec. | Yr. 
PC. ste Oats 778 r.7| 7.7|13-6|16.8|x5 .6]11.6) 5.3|—2-8 —9.8 2.1 
The average maximum temperature for the ten years 1896- 
1905 was 30.1° C.; the average minimum for the same period was 
—34.9°C. The mean monthly temperature was below o° C. for 
five months, and the mean monthly minimum below o° C. every 
month except June, July, and August. The growing season is thus 
short, including about four months, or even less, between the 
middle of May and the middle of September. The long northern 
period of daylight compensates somewhat for the short season. 
TABLE II 
NORMAL PRECIPITATION AT PorT ARTHUR FOR THE 20 YEARS 1888-1907 
Year 
| yan. Feb. May July | Aug. | Sept. Oct. | Nov. | Dec. 
act Bada romdeges Peewee |t-77|t-31|2.44|4.18)5..56|7-67\9.82|7.7/8.23/6.49|3.15|t.77|60.16 
Mar. |April June 
It is here seen that the greater part of the precipitation takes 
place during the growing season; 39.05 cm., or more than three- 
fifths of the total, occurs during the months May-September. The 
snowfall is rather light; during the six years 1900-1905 the average 
was 61.03 cm. Reduced to water this amounts to a precipitation 
of 6.1 cm., which is about one-tenth of the average total for that 
period. 
The evaporation rate is doubtless low because of the low 
temperature, but there are no data available. This and the rela- 
tively abundant precipitation during the growing season seem 
adequate to account for the extreme mesophytism of the forests 
of the region. ‘ 
Since 1906 temperature and precipitation records have been 
kept during the season of navigation by Captain MALonE at the 
lighthouse on Menagerie Island. This is one of the Isle Royale 
archipelago situated 4 km. distant from the nearest point of the 
main island. During the summer of 1910 I kept thermograph and 
rain gauge records at Park Place. There is therefore opportunity 
