36 
IOWA ACADEMY OF SCIENCE 
Agrovyron repens L. Quack Grass. 
The vegetative reproductive organs are commonly called roots by the laity, 
but are universally regarded as rhizomes by botanists. A study of the general 
morphology and histology leaves no doubt as to their stem characters. 
Roots. The whitish fragile roots of the rootstock vary in number and they 
spring from below the scale. 
Rhizome. The rhizomes are generally horizontal except where the stems 
grow toward the surface of the soil, occuring from one inch to 4-5 inches below 
the surface of the soil. The greater majority, however, are found not more 
than three inches from the surface. The creeping rhizomes are from 1 — 3 feet 
long nearly terete, divided into nodes which are from an inch to two inches 
apart; at the nodes numerous small roots and buds spring from beneath the 
scales. 
The histological structure of the rhizome is as follows: The epidermal 
layer consists of thick walled small epidermal cells. Underneath it is the 
hypoderm, of two or three layers of cells, also thick walled. Between the 
vascular ring and hypodermal layer are the large cortical parenchyma cells 
and the endodermis very much thickened toward the vascular bundles. A short 
account of the histology of the rhizome is given by Fluckiger^®. Sayre^^^’ figured 
the stem, giving no description, while Greenish^® gives a short description, and 
a small, unsatisfactory figure. The fibrovascular bundle is of the closed col- 
lateral type, consisting of two or three, sometimes four, large tracheae and the 
small phloem patch between and a little above the tracheae. 
To Dr. Trelease of the Missouri Botanical Garden, to Dr. Beal of Lansing, 
Mich., and to Mr. R. I. Cratty of Armstrong, Iowa, we are indebted for aid in 
securing some of the material used in this paper, and to Miss King for some 
drawings. 
•■**^Pharmacog:raphia. A History of the Principal Drugs of Vegetable Origin met with 
in Great Britain and British India. 729. 
39A Manual of Organic Materia Medica and Pharmacognosy. (Ed. 2.) 440. f. 298. 
^oAn Introduction to the Study of Materia Medica. 310. f. 151. 
