192 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



likelihood that tip multiplicity is recorded in the xylem. (3) The 

 presence of a lateral bud, lateral branches, or pistillate cones at the 

 base of an outer bare zone does not signify multiplicity in diameter 

 growth. In later years, therefore, branches do not necessarily arise 

 from intra-annual nodes. With one exception, however, branches with 

 multiple diameter flushes possessed branches, buds, or cones at the 

 bases of the outer bare zones of the particular year. 



The relations between tip and diameter flushes in angiosperms re- 

 semble those in gymnosperms except that the transitional forms in tip 

 flushes are revealed by leaf scars among angiosperms. Examples 

 come from daily observations and weekly measurements in Maryland 

 at the northwest border of the District of Columbia. 



On WCh I, leaves were out 1.5 cm. by March 25, 1944; by April 

 2.(i, tip growth averaged 5 to 8 cm. on the tree as a whole; and by 

 May 21, it varied from less than 8 cm. up to 47 cm. Tip growth had 

 attained 60 cm. as a maximum by June 4, but by then about half the 

 branches showed two tip flushes in 1944 growth. The second tip flush, 

 which represented from 40 to 70 percent of the total growth for the 

 season, had developed within the two weeks previous to June 4. Soon 

 after June 4, a storm felled the tree with a clean break below ground 

 level. The stem was constricted at the break to half its diameter at the 

 surface, a handicap no doubt seriously interfering with the passage of 

 food and water and perhaps responsible for the cessation of growth in 

 certain branches. 



Tree WCh 2 began growth and followed a course in most ways sim- 

 ilar to WCh I. By June 4, 1944, tip growth on the tree in general 

 varied from 66 to 71 cm. From June 24, which had a few showers, 

 there were high temperatures and no rain until over an inch of rain 

 fell the night of July 13. Another heavy rain fell the night of July 

 19. By July 23, certain branches had started a second tip flush. Other 

 branches had had continuous growth whereas still others had set small 

 terminal buds. On one branch the leader was growing while its side 

 twigs were in various stages of bursting their terminal buds. Second 

 flushes reached a length of 4 cm. by August 6. They appeared to be 

 active for another month but did not gain perceptibly in length. The 

 leader mentioned for July 23 continued to grow, whereas the side 

 twigs showed no growth beyond initial stages of bud opening. By 

 October i, tip growth had been completed. By October 22, very few 

 leaves had fallen. Most of them were brown and crisp with reddish 

 veins and had completely fallen from the tree by October 29. In 

 marked contrast to these older leaves, those on the second flushes were 



