CHURCH: THE BULB IN COOPERIA DRUMMONDII 349 
at points not visible to the naked eye. The ripples in individual 
cells are not confined to radially placed cell walls, as Rimbach 
finds them to be in the species which he investigated. On the 
contrary they may be found on walls running in any direction. . 
In some stages they are so fine as to be distinguishable only with 
the oil immersion objective, but always numerous cells with rippled 
walls may with care be detected in the parenchyma cells of the 
root with a combination of 10 ocular and 8 objective. 
The warped and altogether disorganized condition of the epi- 
dermis and ‘‘hypodermal’”’ layers in the contracted roots of 
Cooperia Drummondii may be comprehended, if we study the 
tissues represented by the blackened areas in FIG. 17, section I. 
It seems safe to accept these facts: (1) roots do shorten; (2) 
the parenchymatous tissues of the root are the seat of this activity; 
(3) the cork and the vascular trace are passive; (4) the cork is 
ultimately crushed; (5) there is a region where one can see wrink- 
lings and measure shortening, a second region where no wrinklings 
are visible yet where one can measure shortening, and an un- 
changed region (Rimbach); (6) in dicotyledons the trace becomes 
visibly curved inward and outward in a wavy fashion, while in 
monocotyledons the vascular bundles remain practically straight 
(De Vries). : 
What remains to be determined constitutes a problem of 
botanical research as yet unsolved. We may hope that some 
worker with an interest in morphology as well as physiology 
may master this problem by a study of serial sections of young 
roots and a consideration of the physical relation of turgor and 
biochemical alterations in the protoplast and cell membrane. 
All the roots of a plant may not shorten equally. Phaedranassa 
chloracea, according to Rimbach (25), has a main root which shows 
no shortening. In other cases none of the roots shorten. Tulipa, 
according to Déring (6), is a case in point. The bulb here would 
not be pulled down since its roots spread out almost parallel with 
the surface of the soil. 
THE SCALES 
The scales, that is, the leaf sheaths, which constitute the 
greater portion of the bulb, are differentiated into certain tissues, 
represented diagrammatically in Fic. 7. Ascale has an epidermal 
