I9I2] BROWN— PINUS RIGIDA 397 



ciably, while greater increase of wood forination resulted as a 

 natxiral sequence. 



Before siunming up the results of the preceding paragraph, some 

 observation on cessation of cambial activity should be given. It 

 has long been recognized that while cambial activity makes itself 

 manifest in many trees at about the same time, there is no relation 

 evident in its cessation. Thus Buckhout (2) foimd in Larix 

 decidua that there was little if any growth after July, while Pinus 

 Strobus continued to form wood until well into September. R. 

 Hartig (6, 7) also gives data bearing on this subject. In beech 

 it lasts 2 . 5 months, in oak 4 months, in Scotch pine and Norway 

 spruce 3 months. Friedrich (see Wieler 14), on the contrary, 

 claims that in coniferous and hard woods in general there are two 

 periods of growth, one lasting xmtil about the end of May, sinking 

 untU the middle of June, and reaching a maximum again in July. 

 Complete cessation residted by the middle of August. The 

 majority of workers, however, unite with Hartig in sajdng that 

 cessation of cambial activity varies greatly with the species con- 

 cerned. 



In the present studies, the latest cuttings in 1909 were made 

 on July 6 upon tree III. At that time growth was still in progress 

 throughout. Comparing these with cuttings taken from the same 

 tree on February 21 of the next year, the following interesting 

 results are obtained. Cutting 2 showed o . 5 of the ring complete, 

 cutting 4, 0.6, cutting 8, 0.85. R. Hartig (6) agrees with T. 

 Hartig (8) that cessation of growth begins first in the crown in 

 trees in open stand and proceeds gradually downward. If such is 

 the case, the data just given present an anomaly, or else growth 

 was accelerated in the apical portions after Jime 15. However 

 some of Hartig's data are in accordance with that already given. 

 For example (Busgen 3), on Jime 21 the ring of an oak as compared 

 to that of a previous year gave the following data: 



At 1 .3 m. height 0.45 complete 



At 3.5 m. height 0.45 complete 



At 5 . 7 m. height o. 45 complete 



At 7.9 m. height 0.72 complete 



At 12.3 m. height o. 57 complete 



At 14. S m. height o. 56 complete (3-4 year branch) 



