1897.] Botany. 61 
while it is the reverse with places on the north side; but why such a 
great difference in the vegetation at the east and west ends? Is it not 
due to something else than climate? Let us see. At Buffalo the mean 
temperature in summer is about four degrees lower than at Sandusky. 
In the spring months the difference is even greater, being five degrees 
in April and nearly five in May and in June. The prevailing winds 
are from the southwest, and traverse the lake for nearly its whole length 
before reaching Buffalo, keeping it cool insummer, the temperature not 
having exceeded 92° since the establishment of the weather bureau 
there twenty-six years ago. Moreover, at the opening of spring the 
wind takes the ice with it to the east end of the lake, where it remains 
so crowded as to prevent navigation three weeks or more after Sandusky 
Bay is clear. The average date of the last killing frost in spring at 
Sandusky is April 30th, at Buffalo, May 20th. Moreover, Buffalo is 
not, like Sandusky, so situated as to be protected from cold northwest 
winds in autumn. Its first killing frost comes on an average September 
15th; but at Sandusky it is not until October 24th—thirty-nine days 
later. The summer at Buffalo, counting the time between the average 
dates of killing frost, is about two months shorter than at Sandusky— 
118 days at Buffalo, 177 at Sandusky. 
The fact that a number of plants belonging to the Sandusky flora have 
been found nowhere in Canada, except on the southernmost points, viz., 
Pt. Peleé Island and Pt. Peleé, which must enjoy nearly as much im- 
munity from frost in spring and autumn as the United States shore 
immediately to the south of them, implies that the climate elsewhere is 
too severe for them, and probably for most of the 118 Sandusky plant 
that are not known to grow in Canada at all. The influence of the cli- 
mate is further shown by the fact that besides 103 species which have not 
been found in Michigan at all the Sandusky flora includes a number 
that have been found only in the southern and especially the south- 
western part, where Lake Michigan affords them some protection from 
ost. 
It is interesting to observe that the protection from frost afforded by 
Lake Erie scarcely extends beyond the counties that border upon it, 
and as a result we have many plants in these that have not been re- 
ported from any other county north of the middle of the State, and 
quite a number that have been found nowhere else in Ohio except in 
the southern part, within forty miles of the Ohio River. Even so far 
south as Columbus the first killing frost in autumn occurs on an average 
six days earlier than at Sandusky. 
