260 BOTANICAL GAZETTE [octoBER 
often matured cells of the leaf or cortex quite as able to form new 
organs as the cells of the meristematic apex of the shoot. In many 
cases, as Tolmiea Menziesii, Cardamine pratensis, Asplenium bulbi- 
jerum, Cam ptosorus rhizophyllus, in the ordinary course of develop- 
ment vegetative growing points arise on the leaves as well as on the 
shoot, and produce new members in the same way. As a rule, the 
more luxuriant the growth the more of these buds will be organized 
‘and develop; but usually, as in Tolmiea, even under the most favor- 
able conditions not all the leaves on a plant will produce shoots. 
But I have found in this plant that every leaf produces a shoot when 
separated from the plant. In Bryophyllum crenatum there are 
numerous growing points along the margin of the leaf which do not 
usually develop further. They bear a similar relation to the grow- 
ing points of the shoot as do the young axial buds of Salix to the 
growing point; for when the influence of these shoot buds is 
removed, those on the leaf form shoots. 
On the other hand, in such leaves as Begonia the cells do not 
start to exercise this reproductive power by organizing growing 
points so long as they are in connection with other growing points 
of the plants; and GorBet showed that in Begonia, upon the removal 
of all the growing points of the stem, the leaf will organize them. 
The same principle holds for other parts. In many rots the 
capacity for shoot development is expressed in the formation of 
“suckers,” as in willows and other trees; but in other plants, prob- 
ably the majority, as in Taraxacum, this ability seems able to expre 
itself only when the influence of the shoot above has been removed. 
Protoplasmic continuity from cell to cell throughout the entre 
living plant may fairly be accepted as demonstrated and the ea 
of various stimuli, either accelerating or retarding, emanating from 
different masses of tissue and affecting other even agi 
remote tissues is not at all impossible. Indeed, such a transmission 
of stimuli necessarily occurs in many of the tropisms, where . 
receptive region is separated by some distance from the region 
response. The whole development of the plant body aera 
involves the suppression of many and the development of ee 
few, either actual or potential, primordia; and the means by war 
this is accomplished (correlation if we must have a name) unde 
