1905] Mc CALLUM—REGENERATION IN PLANTS 251 
below them from developing, but does not influence those above 
them. 
Here we are dealing with growing points already laid down, but 
the same principle holds where these do not exist. If we place a 
root of Taraxacum in a moist condition, the buds at the top will 
soon develop; but if we remove all these buds, entirely new ones 
will be organized and develop. If these be prevented from growing, 
lower down others will be organized, as GOEBEL has shown (2, p. 
492). Here the organization of new shoot primordia along the root 
does not occur so long as those at the top are allowed to grow. Here 
again we cannot attribute this to the monopolizing of the food or 
water by the upper part, for these are abundant everywhere. There 
is a direct relation between the growth of the shoots at the top and 
the non-formation of buds lower down, entirely independent of these 
two factors. 
The development of new roots when those present are removed 
shows a similar phenomenon. The behavior of Phaseolus in this 
connection may be briefly mentioned. Plants grown with roots in 
Water cultures developed a vigorous root system. From some of 
ese all the lateral roots were removed, leaving only the main root. 
Soon numerous new lateral roots arose and grew. vigorously; these 
Were cut off and still others came on, though not so vigorously, In 
the mean time no new lateral roots had come out among the older 
ones on those that had not been so treated. If we cut off the main 
Toot transversely, numerous roots arise just above the cut; and if 
We cut away the whole root system by severing the stem at the base, 
Rew roots arise on the lower part of the stem. Sometimes the roots 
Pi So numerous here that I have counted eighty-one coming out of 
.. Tae” of a Phaseolus stem less than 5™™ in eae 
. a: almost impossible to produce roots on any part of He € 
on - in direct connection with roots below, but when this 
ag 1s broken roots promptly start. 5 
nba a 46.—Local regions of several stems were surrounde 
iia eam cylinders, as in fig. 4. On some the roots were 
ia *e a rom others the stem was cut off at the base. The fue 
still att er ends of the stems were in water. On those with roo 
ached no roots formed on the part of the stem surrounded by 
