190 



ing of fruits the dates of ripeiiino- 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 1st 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 1st 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 elscAvhere 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 



