Rhodora 
JOURNAL OF 
THE NEW ENGLAND BOTANICAL CLUB 
Vol. 9. November, 1907. 
No. 107. 
AN ALPINE VARIETY OF HOUSTONIA CAERULEA. 
ARTHUR STANLEY PEASE-AND ALBERT HANFORD MOORE. 
THE striking white flowers of Houstonia caerulea in Tuckerman’s 
Ravine have long attracted the attention of the numerous persons 
who travel through it every year, whether botanists or not, since these 
flowers form a very conspicuous part of the flora of the ravine.t The 
beautiful white color of the corolla, and brilliant yellow of the throat 
and upper part of the tube have for a long time led the authors to 
wonder if the plant in question might not be distinct from the lowland 
species. Several collections and a careful study at the Gray Her- 
barium have confirmed this suspicion. 
The variety of Tucke:man’s Ravine and the Alpine Garden may be 
readily distinguished by the color eharacters above referred to, together 
with the shape of the corolla tube. In the case of the alpine variety, 
the tube tapers gradually downward from the limb to the base without 
any striking differentiation into a broader and narrower portion. In 
the common variety, on the other hand, there is a long, straight, much 
more exserted tube, and then an abrupt, but usually narrow, funnel- 
like broadening just beneath the border. The following measure- 
ments, while not practicable for purposes of identification, are inter- 
esting evidences of the distinctness of the two phases. A careful 
series of measurements of the breadth of the corolla-tube at the widest 
portion, immediately below the limb, and the total length of the tube 
shows that, while individual measurements in both plants overlap, the 
averages are quite different. The average width in the mountain 
variety was found to be 2.04 mm. and the average length 3.41 mm. 
In the lowland plant these figures were respectively 1.80 and 4.58 mm. 
1Cf, G. S, Miller in Proc. Bost. Soc. Nat. Hist, xxvi, 178 (Feb. 7, 1894) foot-note, “A 
very large, pale form, apparently distinct from the lowland plant,” 
