FASCIATION IN FIELD PEAS. 
75 
of the tube form of the stem may have had its origin in the 
overtopping of the true growing point of the stem by the lateral 
units or branch rudiments, each of which assumed the functions 
of the displaced tip, and all were united into a tube through the 
actively dividing cells at the base of the short stalk or elevation 
belonging to each separate growing point. This possible origin 
of the tubular form of stem could only be verified by the rare 
chance of finding a stem in a sufficiently young state to show the 
tip still united to the adjacent walls, and the actual growing point 
still recognizable at the apex of the tapering tube. 
This suggested mode of origin is offered as explaining the cases 
of fasciation here considered better than that suggested by H. S. 
Conard in the case of sweet potato :* supposing a stimulus to act 
radially upon the apical meristem. If, as is here assumed, the 
apical cell becomes overtopped by the outgrowths from the sur¬ 
face of the terminal cone of the shoot, as figured in normal form 
in Sachs (Physiology, p. 467, 468), no change in direction, from 
linear to radial, is needed on the part of the disturbing stimulus. 
On the contrary the only requirement is that the rudiments of the 
leaf and flower units produced as outgrowths from the meristem 
shall receive a sufficient stimulation to cause them to exceed the 
elongation of the true tip. The nascent nature of the cells from 
which these protuberances arise causes the development of the 
tissue necessary to unite the several growing points so formed 
into a tube, which by the death or failure of any group of these 
connecting cells would form a flat or ribbon fasciation. Under 
the stimulation each of the shoots or growing points continues 
to elongate and produces the outgrowths which the tip would 
have produced and the excessive number of the flowers is thus 
accounted for. The development of flowers instead of leaves 
from the multiplied growing points bears some relation probably 
to the crowding of the young parts upon the rim of the tip. The 
endeavor to propagate under the given conditions resulting in 
the floral rather than foliar growth, the flowers so produced being 
apparently normal, in respect to the several parts, although prac- 
* Publications of the University of Pennsylvania, New Series, No. 6, 
“ Fasciation in Sweet Potato,” pp. 205-215, pi. xix. 
