HARSHBERGER: PHYTO-GEOGRAPHIC SKETCH 157 
MacM., Trifolium repens L., Lepidium Virginicum L., Equisetum 
arvense L., Ambrosia trifida L., Rhus glabra L., Phytolacca decan- 
dra\.., Nabalus altissimus (L.) Hook., Asclepias Syriaca L., Ox- 
ais stricta L., Onagra biennis (L.) Scop., Ambrosia artemisiaefolia 
L., Rhus radicans L., Bidens bipinnata L., B. connata Muhl.; 
Verbena hastata L.., Solanum Carolinense L., Panicum capillare 
L., Agropyron repens (L.) Beauv. Polygonum aviculare L., P. 
Pennsylvanicum ., Amaranthus graccizans L. (A. albus L.), 
Convolvulus Sepium L., Commelina Virginica L. 
Western North America. — Helianthus annuus L., Rudbechia 
hirta L.. 
India. — Adutilon Abutilon (L.) Rusby. 
RUDERAL-PLANT FORMATION. —-It is a difficult matter to dis- 
tinguish clearly between the roadside plant formation and the 
ruderal plant formation, because near our large cities the condi- 
tions influencing vegetation are nearly similar along the much fre- 
quented highways and the neglected waste areas, or rubbish heaps. 
Ruderal areas are distinguished rather by the absence of certain 
plants found by the roadside and by the numerical frequency of 
the species, than by a difference in the component plants. The 
ruderal plant formation may be said to consist of those plants 
which will grow on rubbish heaps, or on made ground formed by 
ashes and other dry material representing the waste of a large city, 
ortown. Such dumping places are found usually near the out- 
skirts, and the material, as it settles down, is first covered with a 
rank growth of weeds and other coarse plants. Later such areas 
are divided into building lots. All of our large cities afford exam- 
ples of such waste heaps and fields. The association of species 
depends largely on chance. It is determined by the way in which 
_ Seeds, roots and other plant material are heaped together in the 
Waste. Near Philadelphia the following plants are most abundant 
in the ruderal formation : 
Plantago Rugelii, Linaria Linaria, Daucus Carota, Rumex cris- 
pus, R, obtusifolius, Verbascuin Thapsus, Arctium Lappa, Xanthium 
Slabratum, Lactuca scariola, Melilotus alba, Carduus lanceolatus, 
atura Stramonium, Datura Tatula, Syntherisma sanguinalts, Chae- 
tochloa glauca, Atriplex hastata, Chenopodium album, C. anthelmin- 
thicum, Amaranthus spinosus, Cichorium Intybus, Melilotus officinalss, 
