The anomalous complexity of the annual rings of young trees which generally disqualifies them from use in growth studies is, in P. resinosa, found to arise from a remarkably thorough organization of ring width and therefore of cambial activity in the tree under the influence of intrinsic determinants. The pattern is manifest when the widths of the internodal wood rings of a single year are followed in sequence from internode to internode down the tree from the apex. A similarly patterned view of the rings is obtained when the ring widths are traced in the ring sequence, conventional for growth studies, that passes from ring to ring in a given internode. The controlling intrinsic factors are held to be nutritional gradients in the axis inferred from the distribution of foliage and light along the axis of trees growing in the forest and in the open.In both types of sequence the pattern obscures the variations induced by random extrinsic factors and severely limits the value of these sequences for examining the effect of such factors. This disability can be avoided by the use of a third sequence of ring widths in which each term is the width of a ring which was laid down in an internode different but of the same age at the time of ring formation as the others in the sequence. Such sequences have never been used in growth studies. Yet they are found to be unpatterned and the effect of the fluctuating extrinsic factors can be examined effectively in them and in them alone.The complex relation between the responses of the cambium thus determined and those of the apical growing point to the random extrinsic factors is found to derive from the discontinuity of terminal growth introduced by the winter pause between bud formation and axial extension. These two stages of terminal growth are influenced by the extrinsic factors of the two different years. The effect on the cambium is simpler than this but is determinably related to that on the apical growing point.The results afford the ground for a first advance toward the removal of the disqualification of the use of young trees in studies of growth and of its factorial control.

The main shoot apex of P. resinosa is found to comprise four groups of meristematic cells constituting four generative centers by which the parts of the winter terminal bud are laid down. These are the superficial initiating cells, the group or zone of subapical mother cells, the zone of pith mother cells, and the flanking cells.The superficial primordia of the terminal winter bud pass the winter as secondary lateral budlets on the flanks of the main bud axis. Those of the leaf-bearing short shoots do not normally differentiate leaves until the following spring. Neither do those which develop into lateral long shoots. The fertile budlets, on the contrary, produce cones in the late summer and autumn. The female cone enters the winter with no tissue differentiation of the cone body. This takes place very slowly but prominently in the course of the winter. The male inflorescence is well advanced in the autumn and winter progress is relatively slight.The natural control of morphogenesis at the shoot apex including the fitful seeding habit of P. resinosa is considered in the light of the growth timetable. To explain its mechanism, a working hypothesis involving production, consumption, and concentration of auxins is advanced as a preliminary to future work.

Fw0 Ilieasures ;LIT 11i:ecl~d to de~crihe ln~~nlerici~llp the csctivi t y of t h e interiiodal cam1)iuan ill terms of a~lnuaH increnlc~it. 7' 11ese are "specilic wood volrt~lle i~i c r e m~~l t " , a measure of ;~cl t IiCl t oelr ~~i-o(-etlelr-t>s clrld conce~jts n-ere ~I C B I I~ put to the test i 11 illd~xg,cli i~itc-~lsi\.c. I;iiicl will 1 )~ rrelcdetl to ;\c.bic\~c. a falllj, s,ltisf;~c.tor)~ cl:~rific.atio~l of c.vtlia tht> ~r~c'hiiic.~rl ~)i-o%,lc~~ns iiivcslvt~ci iii growtkr studicls oh' this ch,ir;lctcr.In the coursc oi oalr \vtsrl< ~v c a-otlltf 11ot fail to IIC 11111)r~ss~cI 1)). thy cll~iiostirlc-rcclible f,lc-t that tlaoelgha trecLs of geomet ric,ll li;lL,it suc.11 as Y. re~i71u.s(1 it'0111(1 :lpl)car to be ;LIB1OIlg the most ile:~rlj~ idc,~l of livi~ng orgalrisms i l l 1vhic.h t o exanii~ne problems of biologic.:rl growth, j 7 t ' t , the cliornlous litor,~t ur-c1 of t n-c.e growth has c.oriti.ibtiteti little or ~l o t h i~i g to the c o~-a~~) a r ;~t i \~e st url!. of gro~vtla.'I'he reasolr for this wc-~~lld seer...

The analysis of growth of a pine tree has been estended to include the primary branches, and this paper reports observations on radial gro~vth, as espressed by ring width.Trees from contrasting situations are compared, and the deliberate release of one tree from suppression permits the attribution of specific changes in growth to the change in evternal condition of the tree.The primary branches provide a series of axes that automatically undergo a change in nutritional status, although the distal portions of all of them are produced sirnultaneously. Every primary branch is initiated a t the apex of the tree and each year is overlaitl by one more whorl of branches; so it advances t o a relatively lower position in the tree each year, and itself adds one more internode.The upper branches and those portions of lower ones that were formed while near the top of the tree repeat the pattern and configuration of growth in the main asis. Advance of a branch to an inferior position is associated with severe suppression and a redistribution of growth gradients.

The distribution of photoassimilated carbon-14 in young plantation trees was studied 6 or 10 days after supplying 14CO2 for a day to a single branch in the second, third, or fourth whorl. Both apical and cambial growth occurred during the interval, and apical growth throughout the trees was measured. Elongating terminals and products of cambial growth in the fed branch were highly labeled. In all trees some 14C was exported to the adjacent side of the tree. Movement in the trunk was bidirectional, but the position of the donor branch determined the direction of major transport. Only from whorl 2 was it upward; from whorl 3 or 4 it was downward. In both directions activity decreased with distance from the base of the donor branch, and the leader did not accumulate more, per unit weight, than the intervening internodes. Some 14C entered branches arising in the path of transport.Radioactivity was concentrated only in regions of growth, whether apical or cambial. Most of the 14C was in ethanol-insoluble compounds, largely in cell wall constituents. Autoradiographs of stem sections confirmed that 14C was deposited in currently developing tracheids of secondary xylem during most of the 10-day growth period. The ratio of activity in lignin to that in cellulose was inversely related to the total 14C in the cell wall constituents.