BULLETIN 
OF THE 
TORREY BOTANICAL CLUB. 
Vol. XIX.) New York, May 5, 1892. * [No. 5. 
- A Century of American Weeds. 
THEIR ROOT SYSTEMS TABULATED. 
By Byron D. HALSTED. 
Weeds, it is claimed, do their greatest damage to crops by 
Tobbing the soil of those food elements that would otherwise go 
tothe building up of the legitimate plants. If this be true, and 
the conclusion is a reasonable one, it follows that the root system 
of these « Sappers and miners” is of special importance. 
_ During the past summer, in the making of a collection of a 
hundred worst weeds as an economic herbarium to be distributed 
to the agricultural colleges, experiment stations and other insti- 
tutions, particular attention has been given to the subterranean 
Portion of each species, and with very few exceptions the root 
system, entire as possible, is shown with each specimen. In this 
_ fespect the collection is unique, thanks to the untiring patience — 
_ and deftness of Mr. J. A. Kelsey, my assistant, who has per- 
formed in large part the painstaking labor of collecting, pressing, 
and mounting the specimens. 
A Prolonged study of the century of specimens, or more ac- 
Surately the fifty or more specimens of each of the hundred 
Species, has led to a classification of the root systems as present- 
ed in the accompanying table. The first division of the plant is 
"pon their duration, namely, into those with perennial, those 
With biennial, and those with annual roots. Next, under each of 
_ these heads the root systems are again divided into those with 
'ap-root prominent, with roots in a cluster (fascicled), and 
those with the two systems more or less evidently combined. 
“der each of these heads the roots are again classified as to their 
