191 2] BROWN— PINUS RIGIDA 393 



period of two years, it would appear that in the vicinity of Ithaca 

 growth began in Pinus rigida at about the same time each spring. 

 To determine this point definitely, however, observations must 

 needs be carried on for a period of years. That growth made itself 

 evident in 19 10, however, as early as April 15 is readily apparent 

 from the photographs. 



Place of cambial awakening 



The question of origin of growth is still in dispute. T. Hartig 

 (8) claimed that it made itself manifest in the youngest branches 

 first and extended slowly downward. Nordlinger {Forest Botany, 

 1874) makes the same assertion. R. Hartig (7) appears to accept 

 his father's statement if we are to judge from the following quota- 

 tion: "Am oberirdischen Stamme beginnt der Zuwachs zuerst in 

 den jiingsten Trieben," etc. These three investigators, therefore, 

 were unanimous in the opinion that the awakening of growth is 

 earlier at the top of a tree than below. 



Mer (10) disputes this general assertion. According to his 

 researches, the procedure of awakening was sensibly different in 

 older trees. While in 25-year-old oaks, beeches, and firs, growth 

 was first manifest in the youngest branches, in the older trees it was 

 in evidence at the same time at the bases of the branches and even 

 in the trunk where the roots began. From these points growth 

 gradually extended to the intermediate regions. 



Figs. 4-6 correspond respectively to those of the preceding 

 numbers, except that a period of 19 days intervened. Comparing 

 those of different date, we see that growth is more in evidence in 

 every case where the cutting was taken at the later date. In figs. 

 I and 2 we have apparently the resting condition, while figs. 4 and 

 5 exhibit signs of growth, the latter being more in evidence in fig. 5. 

 Comparing figs. 3 and 6, it follows that there is a considerable 

 advance in growth. In the former, at the outside, only two half- 

 formed tracheids are to be seen, while in the latter three or four 

 rows are present and these are of larger size. Comparing figs. 1-6 

 as a whole, it is evident that during a period of 19 days there was 

 an awakening of cambial activity in the apical portion, first manifest 

 in fig. 3 on April 15. Growth first appeared in the crown of tree III 



