I have also found Pellaea atropurpurea growing thinly, on a dark red sandstone, at Paris Springs, Missouri, not far from Springfield.
I would like to add to the localities of Polypodium vulgare in Michigan. I found it, in the summer of 1910, growing in dense mats on sand dunes, south of Macatawa, Michigan. The plants were in a woodland composed principally of hemlock, with oak and a general mixture of elm, maple, hickory, etc. When you lifted a mat of the fern, the bare sand was left exposed. I thought the conditions rather peculiar.
I found many ferns growing on these wooded sand hills where, at the most, there was but half an inch of soil on top of the white sand. The list includes:
Adiantum pedatum; Pteris aquilina; Asplenium filix-foemina, in marshy places between the dunes; Polystichum acrostichoides, very sparingly; Nephrodium thelypteris, very luxuriant, like the lady fern, in marshy ground; Nephrodium marginale, the most common fern; Nephrodium cristatum; Nephrodium spinulosum, wherever there was a rotting chunk of wood; Onoclea sensibilis, and Onoclea struthiopteris, both very rank; Osmunda regalis and Osmunda cinnamomea, these last four in marshy spots; and Botrychium virginianum, on the sides of the dunes.
I have been observing the habits of Onoclea sensibilis for many years, even raising plants from the spores to five years old; caring for other plants for years, changing conditions, and varying my experiments, until I have come to the following conclusions:
When the soil is constantly and evenly moist and unusually rich, and the plant is constantly shaded, it tends to produce its fertile fronds flattened out like the sterile, with all stages to those only partly rolled up. These unrolled fertile fronds do not differ from the rolled up ones, on the same plant, except in this one particular.
When a heavy screen was changed so that the plants would be in the full light and sun, the fertile fronds produced the rest of the season were as tightly rolled as usual, and it took two years of shading before these plants produced open or unrolled fertile fronds again. Varying the other conditions—moisture and nutriment, had similar results, but less marked.
Champaign, Ill.
SCHIZAEA PUSILLA AT HOME.
Anyone who has seen this odd fern growing in its native haunts will probably concur in the opinion held by some, that while it is looked upon as one of the rarest of ferns its small size and its habit of growing in the midst of other low plants have no doubt caused it to be passed over by collectors in many regions where it really exists. This should be an encouragement to collectors to keep the fern in mind in their field excursions with a view to adding new stations for it to those now known. The finding of a rare plant in a new locality is always a source of especial pleasure to the discoverer, aside from being an item of value to the botanist in general.