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plete possession of the habitat. Shade conditions are such as to exclude 
light-demanding forms. First attempts at photography under the arbor 
vitaes resulted in failures, on account of uniform under exposures. The 
vegetation of the forest floor is not abundant, except in early spring. The 
herbs are largely shade-enduring species. The mat of roots and fallen 
branches and leaves is another factor that deters invasion from without. 
If the toxicity of the substratum is a factor, it exerts its maximum influence 
here, under present conditions. Then, too, the plants of the association are 
reproducing themselves very efficiently, all stages of seedlings and saplings 
being found. Nearly all the Thuyas germinate on stumps and logs. A 
specimen four or five inches in diameter and twenty-five feet in height was 
found growing on a stump four feet high. Even the oldest trees, which must 
be hundreds of years old, are still grasping in their roots the partially decayed 
remains of the logs upon which they germinated. The fact that the logs 
are lying in a position that subjects them to the greatest exposure to decay 
shows the resistant qualities of arbor vitae wood. The logs shown in the 
photograph (Fig. 4) are still fairly sound, though the trees which grew upon 
them are two feet in diameter. 
One of the commonest undergrowth shrubs is Taxus canadensis, which is 
here a prostrate, creeping shrub, seldom more than one or two feet in height. 
No traces of seed formation were observed, but the plant reproduces abundantly 
by layering. What at first glance seems to be a group of plants is found 
to be a series of layered branches from a common central plant. This habit 
is of considerable ecological importance here, since it seems to be the only 
means of reproduction of the species. 
As the accompanying list shows, the arbor vitae association 1s the habitat 
of a large number of species of ferns, which form a prominent part of the 
flora of the association. Camptosorus was found in four widely-separated 
situations, growing luxuriantly upon fallen logs. Plants of Pteris more than 
four feet in height are rather common. Osmunda cinnamomea is common, 
but only two specimens of O. regalis were seen. Botrychium virginianum 
is abundant. Prothallia of O. cinnamomea are common. 
A single plant of Lycopodium lucidulum, probably the last representative 
of its species, was found. The disappearance of this species is indicative 
of what has occurred in the case of many other northern forms and of the 
aventual fate of those that remain. Another disappearing species is 
