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TO MRS. FISHER (_née_ BUCKLEY)


_Frith Hill, Godalming. February 16, 1888._

My dear Mrs. Fisher,--I know nothing of the physiology of ferns and
mosses, but as a matter of fact I think they will be found to increase
and diminish together all over the world. Both like moist, equable
climates and shade, and are therefore both so abundant in oceanic
islands, and in the high regions of the tropics.

I am inclined to think that the reason ferns have persisted so long in
competition with flowering plants is the fact that they thrive best in
shade, flowers best in the light. In our woods and ravines the flowers
are mostly spring flowers, which die away just as the foliage of the
trees is coming out and the shade deepens; while ferns are often dormant
at that time, but grow as the shade increases.

Why tree-ferns should not grow in cold countries I know not, except that
it may be the winds are too violent and would tear all the fronds off
before the spores were ripe. Everywhere they grow in ravines, or in
forests where they are sheltered, even in the tropics. And they are not
generally abundant, but grow in particular zones only. In all the Amazon
valley I don't remember ever having seen a tree-fern....

I too am struggling with my "Popular Sketch of Darwinism," and am just
now doing a chapter on the great "hybridity" question. I really think I