CHURCH: THE BULB IN COOPERIA DRUMMONDII 347 
its individual cells are irregular in diameter, presumably from the 
effects of some pressure. The parenchyma cells outside the trace 
are still equipped with cytoplasm and nuclei, although some force 
has pushed them by each other and flattened their nuclei. 
ROOT CONTRACTION 
The first reference in the literature to root contraction, accord- 
ing to De Vries (34), is that of Tittmann (31) in Flora for 1819. 
Under ‘‘Wurzelbildung”’ Tittmann describes the contraction of 
the roots in Daucus Carota as follows: ‘‘Der Stengel wird dicker 
und kiirzer, zieht sich gleichsam in die Erde hinein, oder wird von 
derselben angezogen, und man findet dann nach einiger Zeit die 
langen Saamenblitter dicht auf der Erde ausgebreitet. Unter- 
sucht man in dieser Periode die Wurzel, so hat sich die Granze 
zwischen ihr und dem Stengel, der sich nun auch in der Erde 
befindet, ganz verloren und ausgeglichen.” 
De Vries :(34) himself worked principally with dicotyledons, 
experimenting with eighteen species of plants. He studied the 
effects of exposure to air, to water and to salt solutions on strips, 
separate pieces of definite tissues, and single cells of roots. He 
measured changes in length, width, and volume of tissues and 
cells. He considered roots from plants still bearing succulent 
cotyledons to those two years of age. He studied young roots and 
roots two years old. Each experiment is considered in itself and 
in the light of previous experiments, until at last he concludes 
that root contraction is not due to intake of water but to changes 
in turgor and remarks that the thoughtful reader will ask, “durch 
welche Ursachen die ungleiche Dehnbarkeit der Zellhaute selbst 
bedingt wird.” 
Rimbach discusses root contraction as it occurs in Colchicum 
autumnale (26), Arum maculatum (28), and Allium ursinum (27). 
He found that, in the case of naturally deep-set bulbs of Allium 
ursinum,a depth of 10-15 cm. was attained after several years by 
the contraction of the roots. In explanation as to how contraction 
in roots comes about he states, that, while the root tip holds firmly 
to the earth particles, the endodermal cells contract longitudinally 
as a result of a tendency to lengthen radially and tangentially, 
which results in the contraction of the root. The bulb yields to 
