148 HARSHBERGER : PHYTO-GEOGRAPHIC SKETCH 
tum (L.) Kuntze (Laportea Canadensis Gaud.), Chelone glabra L., 
Panicum dichotomum L., Lilium Canadense L., Monotropa uniflora 
L., Prunella vulgaris L., Silene stellata Ait., Phryma_ lepto- 
stachya L. 
August. — Lobelia syphilitica L., Solidago bicolor L., Aster 
macrophyllus L., Panicum microcarpon Muhl. 
September. — Aster Jacvis L., Solidago caesia L., Collinsonia 
Canadensis L. 
All of these species are not found in a single wooded area. 
They are distributed in different combinations in southeastern 
Pennsylvania. Thus such local plants as Cypripedium parvifiorum, 
C. hirsutum, Camptosorus rhizophyllus, Galeorchis spectabilis, Hy- 
arastis Canadensis and Leptorchis liliifolia occur only in a few places 
in the region, but they are mentioned because they are plants 
which grow best in the deep shade formed by the crown of the 
dominant forest trees. The vegetal covering of the forest floor 
also differs with the season of the year, so that the spring flora is 
distinct from that of the summer flora, and the summer flora is dis- 
tinct from the autumn flora. In the lists above this succession of 
floras is displayed, as far as the phenologic data at command will 
permit. The woodland species are most numerous in the spring, 
because the conditions are most favorable for their growth. Such 
plants as.the bloodroot, wild ginger, May apple, windflower and 
lady’s slipper abound. The summer flora of the woods is poorer 
in the number of species. Such plants as touch-me-not, cardinal 
lobelia, boneset, all-heal, etc., are found with a number of funguses, 
such as Russula, etc. The autumn flora of the forest consists of 
asters, golden-rods, mints, and a large number of toadstools and 
mushrooms, which feed saprophytically upon the humus of the soil 
composed of leaf-mold and rotted wood. The phenologic distri- 
bution of the woodland species is, therefore, quite as marked 4s 
their geographic habitat and controls associations of species in 4 
most intimate manner. The seasonal sequence of species is one of 
the controlling factors in the struggle for existence. With the 
exception of the rivalry of the root and underground stem systems 
for ground-space, the spring plant may be said not to come into 
competition with the summer- and- autumn flowering species and 
conversely. 
