igiS] BROWA'—PINUS STROBUS 227 



words. WiELER (39) has given some data concerning the termina- 

 tion of growth from the three white pines which he investigated 

 (table J) . In tree I the ring was complete on the north and south 

 sides at the base on September 8. In tree II it was complete on the 

 south side at the same height on August 28, while in tree III it 

 was still in progress on September 8. In general his results indicate 

 that in the vicinity of Dresden, Germany, growth in white pine 

 ceases slightly earlier than at Ithaca, N.Y., a reasonable conclusion, 

 since the former is in a higher latitude. The work of Buckhout 

 (2), already .cited, is of interest in this connection. While his 

 measurements were made externally and are therefore subject to 

 the same criticisms as those of Th. Hartig, certain facts are obvious. 

 During the four years over which his experiments extended, growth 

 was manifest in the white pine during the last 10 days in August 

 and in two as late as September 8. His results serve to accentuate 

 the fact that white pine has a long growing season, much longer 

 than the European larch, with which he also worked. 



The growing season of tree I may be used, in spite of variations 

 which occur between individuals in that respect, as a general indi- 

 cator of white pine growth in the vicinity of Ithaca. As already 

 indicated, growth in white pine may be divided into two periods: 

 (A) growth without cell division and (B) growth with cell division. 

 B of necessity follows A. Considering A and B together, growth 

 began in tree I before March 29, 1913, and continued until after 

 September 19 of the same year, a period of over 5.5 months; and 

 this does not include the late phloem development which without 

 doubt continued into October. Cell division began before April 26 

 of the year in question, and if growth is considered in the narrow 

 sense, the period is shorter by several weeks. If there are any 

 grounds for the statement that trees complete their seasonal growth 

 in a period of 4 or 5 weeks, white pine is an exception to the rule, 

 as here the growing season extends over a period of 4-5 months, 

 depending on the interpretation of the term "growth." 



Dififerentiation in the annual ring in aerial parts 



In working up the foregoing data, no stress has been laid on 

 diilerentiation within one and the same annual ring. As is general!}- 



