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ing of fruits the dates of ripening as predicted by the temperature 
constants have an uncertainty of one or two days only in 94 per cent 
of the cases. In the choice of the date from which to begin taking 
the sum of the mean daily temperatures, it would seem that for 
annual plants the date of sowing the seed would be proper, but that 
for perennial plants the whole winter since the end of the preceding 
growing season would be proper; but instead of the latter, Fritsch has 
adopted that epoch at which the mean temperature of the day has its 
minimum value in the course of its annual variation, and this, com- 
bined with the ease of computation, leads him to adopt the Ist of 
January for all perennials. For the biennials and the annuals he 
would have preferred to count from the time of sowing the seed, but 
as the latter date was frequently not recorded and as most of the 
temperatures are below freezing in the early part of the year, he finds 
no large error introduced by adopting the Ist of January for these 
also, and this is very nearly equivalent to Quetelet’s method of count- 
ing from the time of the permanent awakening of the activity of the 
plant in the spring. 
In the following list I have given all of Fritsch’s results, and with 
reference to the practical application of these figures to the prediction 
of similar phenomena elsewhere quote his statement that he had con- 
vinced himself in many ways that the trees and shrubs observed by 
him in the Botanical Gardens at Vienna blossomed at the same time 
as those in the open country, but for all herbs this is true to a less 
extent, and only in a few cases are the departures important. 
Although many plants do not ripen in the short season at Vienna, 
yet he was able to determine their thermal constants for the date of 
blossoming. 
In general the plants and their seed had by long cultivation in 
Vienna become acclimated to that locality, so that by applying 
Linsser’s theorems to Fritsch’s results they become applicable to the 
phenomena that would be manifested by these plants in other parts 
of the world. 
As concerns the temperature of the soil, Fritsch states that the 
perennial grasses were partly shaded by trees until 1852, after which 
they were cultivated in a sunny spot. The annual grasses were uni- 
formly in a sunny region, slightly inclined toward the north. 
The orders or families, with the genera and species and sometimes 
varieties included within them, are arranged in the table as given 
by Fritsch, who states that it is in accordance with the natural sys- 
tem of Endlicher, which is generally adopted in Austria as prefer- 
able to a chronological or alphabetical. But for the convenience of 
American readers I have added to each of Fritsch’s orders the num- 
ber by which it is designated on pages 5 and 736 of Gray’s Manual of 
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