120 Houstonia caerulea.
Root perennial, sending up numerous, slender, twisted, obscurely
square green stems, about four or six inches high, forked above.
Radical leaves numerous, spathulated, ciliated, and slightly pubescent
; those of the stem opposite, fewer, ovate, ending in a broad
petiole, and becoming narrower as they approach the top of the
stem, until they are sometimes linear-obtuse, and glabrous. Calix
obtusely quadrangular, four-toothed, an eighth of an inch long, acute.
Germ purplish. Flower-buds yellow, and nodding before the flower
expands. Tube of the corolla externally pale, and internally dark-
yellow. Segments of the limb four, ovate, terminating in an abrupt
point, curved backwards, flax-flower-blue, sometimes white, with the
centre white, variegated on each segment by two spots of bright
yellow. Stamens included, pistil just perceptible above the throat of
the corolla, sometimes white. Grows in grassy places on way sides,
the grassy borders of fields, edges of woods, from the northernmost
to the most southern extremity of the Union. Flowering from April
till September. It prefers rich soils, and in such is more robust than
in Sandy and shady places, where it becomes tall and more slender,
with smaller leaves and flowers.
The genus to which this pretty little plant belongs, was named by
Gronovius and Linnaeus after Dr. William Houston, who died in
1733. He was a botanist of eminence who resided many years in
the West Indies, and visited South America between the years 1728
and 1732. He rendered essential services to the science he culti-
2
Houstonia coerulea. 121
vated, by the interesting observations he made on Jalap and other
medicinal plants, as well as by transmitting seeds to Europe.
Wherever this plant occurs, it is abundant. It is admired for
its beauty alone, being quite devoid of fragrance, and has taken
its specific name from the colour of the flowers, which is generally
cerulean-blue, though occasionally they are quite white ; they
are very numerous. Cultivation improves the vigour of the plant,
and perhaps heightens the brilliance of hue in the flowers ; and
it is said that in England, where it has been introduced at Kew since
1785, it is quite hardy, and with the slightest degree of attention is
made to flower perpetually during Spring, Summer, and Autumn. It
is easily increased by parting its roots ; hence it might be a fit subject
for introduction to our gardens, particularly on account of the early
period of its flowering. It is also a native of the western coast of
North America.
The figure represents the plant of its most common size.