The same phenomenon has been observed in other plants. See
observations on _helianthemum_, page 27." Had the doctor given a more
extended investigation, I fancy he would have agreed with me as to the
cause. I found hundreds of diversified specimens. I am not aware that
it was after a rain, but I took up a number of the plants, and always
found a vigorous scaly root bud, undergoing development at this early
season under ground, to produce a new stem the following spring. I
came to the conclusion that, as the temperature was below freezing and
snow was on the ground, the expanding bud, in close proximity to the
surface, gave out sufficient caloric or warmth to generate vapor from
the moist soil. This vapor rising around the stem of the plant, and
attracted by it, becomes congealed into what we term hoar-frost, in
numerous forms; some like shellwork, others like tulips, with radiated
petals, variously contorted, and often as symmetrical as snowflake
crystals.
[Illustration: Root-bud and frost-flower of the Cunila Mariana
(Maryland Dittany). A, the developing or budding root. B, the old stem
of the previous year. C, the congealed vapor or hoarfrost, forming the
first flower of various shapes.
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