26 Nebraska Agricultural Exp. Station, Research Bui. 7. 
hold if the internodes of the terminal inflorescence were included 
as a part of the plant axis, for they are shorter than the internodes 
immediately below them. The axis of the inflorescence is, 
however, so definitely differentiated from the plant axis proper 
that it is not included here in measurements of the latter. 
In plants of indeterminate growth habit the internodes are 
of comparatively uniform length for some distance on both sides 
of the longest internode, but sooner or later they become shorter. 
This shortening of the internodes is slight at first and increasingly 
more marked as growth proceeds. The growth curve for this 
period of retardation is therefore practically the reverse of that 
for the period of acceleration (Fig. 10). 
The larger branches of bean plants manifest in general peculiar- 
ities of growth very similar to those of the main axis. Such 
curves are shown in Figure 11. Branches are as a rule more 
vigorous than the plant axis. This is particularly true of bush 
beans where, as is shown in Figure 11 A and IIB, even the first 
internode of the branches is commonly considerably longer than 
the corresponding internode of the plant axis. It is not un- 
common for some of the branches of bush beans to reach twice the 
height of the plant axis. In Figure IIB is shown a bush bean of 
which the axis was 233 mm. high and a branch from the third 
node of the axis 535 mm. high. In pole beans, tho the branches 
are often somewhat more vigorous in growth than the plant 
axis, they are by no means universally so and very frequently 
grow less rapidly at the start than the corresponding part of the 
plant axis, as shown at C and D, Figure 11. It seems possible 
that the relative rapidity of growth of axis and branches may 
depend in part upon whether the branches start during the 
period of general growth acceleration or retardation and it certain- 
ly depends in part upon the weather. 
Acceleration of growth in the young plant is probably due to 
the fact that the plant is then constantly becoming better estab- 
lished. Its roots are gradually becoming better able to obtain 
water from the soil and its rapidly enlarging leaf area is contin- 
ually becoming better able to supply food materials for growth. 
But why should not this acceleration in rate of growth continue 
indefinitely in plants of indeterminate habit? Above all why 
should retardation in growth rate occur? It is unlikely that 
senility is to be considered in this connection. The heavy drain 
put upon the plant's resources by the development of a crop of 
pods and seeds doubtless has much to do with retardation of 
growth rate. This is particularly true of the smaller pole beans, 
which early set a heavy crop of pods. With the larger and later 
pole beans, the less favorable weather late in the season doubtless 
has a pronounced influence in retarding growth. 
