GEOGRAPHY OF PLANTS. 497 



turation 8,607.66°, wliich accrued by the 21i?t of September, or thereabouts, 

 wheu 8,581.3° were found to have been reached by addition of the daily means 

 for 129 days, at an average of 66.51° for the entire term. Even Avith this ag- 

 gregate it was reported at Waterloo "poor and foxy." The Concord may 

 then be readily grown at Providence, Rhode Island. 



Rebecca, leafing at 53.13^ on 14th May, required 8,900.66° to advance it 

 to maturity. On the 26th of September the sum of 8,906.9^ was attained at 

 Providence in 135 days from date of foliation. If the Rebecca- was fully 

 ripened at Waterloo, it might be equjilly well groAvn at Providence on a warm 

 soil and under a favorable aspect. 



If we suppose the Isabella to bloom at Providence on the 15th of May, 

 when the initial for the Catawba, 52.71°, has been reached, which is highly 

 probable, from comparison of observations at Kelley's island and elsewhere, 

 and that it may matm-e as early as the 15th of October, which is later than 

 the date of the average appearance of frost, and yet not an erroneous assump- 

 tion, we find that between these dates a sum of heat will have accumulated of 

 10,451°. From this we learn that in favorable years when the autumn is warm 

 and the frosts very late that the Isabella may be grown, but that its ripening 

 must in general be uncertain and irregular. 



The Catawba and Anna open their leaves at the same temperature as the 

 Delaware, or thereabouts — 52.71° — but require more than 11,000° Fahrenheit 

 to ripen them — a sum of heat which is not reached at Providence before the 

 appearance of frost, except in very favorable years. As the temperature de- 

 clines rapidly after the middle of October, and killing frosts occur near the 

 beginning of the month, not unfrequently, in the average of twenty-eight 

 years on the 11th of October, the latter-named varieties cannot in general be 

 properly ripened at Providence. 



From the preceding application of the principles derived from the table and 

 comparison of observations made elsewhere from similar data, on which our 

 limits forbid further enlargement, we conclude that the Delaware and Clinton 

 and Hartford Prolific may certainly, and the Concord, Diana, and Rebecca 

 may generally be grown at Providence, Rhode Island ; that Isabella cannot 

 always be perfectly ripened ; and that the Catawba and Anna can never be 

 there matured, unless in the long warm autumn of extremely favorable years. 



Tlie general conclusions are, that the Delaware, Hartford Prolific, and Clin- 

 ton belong to a class of grape-vines which requires for ripening about 8,000° 

 of heat ; that Concord and Diana demand 8,500° ; Rebecca needs about 9,000° ; 

 Isabella 10,000° ; and Catawba and Anna must be grown where they shall 

 receive from foliation to maturity a sum of heat calculated from the daily mean 

 temperatures Avhich must at least amount to 11,000° of Fahrenheit's scale. 

 Unfortunately extensive tabulated reductions of daily mean temperatures are 

 not of ready access. Those made by Professor Caswell at Providence, Rhode 

 Island, we have been enabled to consult while preparing this paper, but much 

 regret that we have not been able to obtain similar valuable data for sundry 

 places over a wide district. The records we have been enabled to consult have, 

 however, been ample for our general purpose — to establish the principle that 

 we can employ the elements of initial temperatures and duration of heat — com- 

 bine the values of temperature and time, for the determination of the possibili- 

 ties of culture in any district, of plants as yet there ixnknown or untried. 



On comparing the table of American grapes exhibiting their dates of leafing, 

 &c., with that in which we have noted the temperature of various places in 

 Europe within and without the wine districts, we observe many points of simi- 

 larity between our native vines and their foreign congeners. By the table of 

 foreign wine localities we learn that at all those places where the mean for the 

 hottest month falls below 67°, the wine is not good or the fruit never ripens, 

 38 A 



