I9I2] BROWN— PINUS RIGIDA 395 



branches, at least in the case of trees standing in the open, appears 

 to be identical with that in the apical shoot of the main axis. 

 Cuttings taken May 4 showed about the same amoimt of growth 

 in each case. 



The time of the beginning of cambial activity at the base of the 

 branches is of interest when compared with that of the main trimk. 

 Fig. II shows a section from the base of a limb six years old. Fig. 

 10 is from a cutting taken from the main axis just above the branch, 

 and fig. 12 a Uke distance below. Growth is most advanced in 

 fig. 12, present in fig. 10, but lacking to all appearances in fig. 11. 

 Cuttings taken from the limb in question showed growth in evidence 

 to the extent of one or two tracheids (out to and including the 

 apical shoot). It follows from the above that growth at the base 

 of the branches is more retarded than at neighboring spots in the 

 main axis. It proceeds more rapidly in the latter than it does in 

 the former, so that it is often in evidence in the main axis before it 

 makes its appearance at the base of the branches. This may be 

 due to the more rapid rise of solutions in the trunk, although 

 further investigation is necessary to decide that point. 



Rate of procedure 



Having determined the general procedure of growth in Pinus 

 rigida, observations were next made on the rate of procedure. In 

 order to make estimates of this, the series of cuttings of 1909 on 

 tree II were employed. There were iour sets of these of twelve 

 each. In each set the amoimt of wood formed for the individual 

 section was determined as nearly as possible with a micrometer 

 scale, and the results tabulated on a basis of 100 (table I). The 

 nvunber of days intervening between each observation are given as 

 well as the total gain and average gain per day; x imphes cutting 

 was a failure ; + signifies width at least as much as given ; ? indicates 

 apparent loss due to local growth fluctuation. 



The table is of value in leading us to certain general conclusions. 

 On May 13, the width of the new-formed ring was greatest in cut- 

 tings 4-6. It gradually dwindled in size toward the apical shoot, 

 while below there appeared to be a decline followed by an increase. 

 The next investigation was made on May 25, twelve days later. 



