516 WOODY PLANTS OF MASSACHUSETTS. 
tains herbs or low shrubs, with simple, usually entire leaves, 
generally opposite.—in a single genus partly alternate,—and 
with or without stipules. The flowers are perfect; yellow, 
white, rose-colored, or red; transient, usually lastmg, except in 
Hudsonia, but a day, often but an hour. The calyx is of 5, 
persistent sepals, the 2 outer usually much smaller, sometimes 
bract-like, sometimes wanting, the 3 inner imbricated and some- 
what twisted before opening. ‘The corolla has 5 petals,—rarely 
3,—sometimes none,—crumpled before opening, and twisted in 
a direction opposite to that of the sepals. The stamens are 
numerous and distinct, with short anthers. The ovary is made 
of 3 to 5 united vessels, surmounted by a single style and 1 or 
more stigmas. ‘I'he fruit is a many-seeded capsule, with from 
3 to 5 valves, with imperfect divisions at the middle of the 
valves, bearing near the central lime the seeds, which are smooth 
and angular, with a curved or spiral embryo in the midst of 
mealy albumen. The properties are not known, except in cer- 
tain species, which exude an odoriferous, balsamic resin, called 
labdanum or ladanum. 
The Cistdcee are mostly confined to the temperate regions of 
the northern hemisphere, and abound especially in the countries 
bordering on the Mediterranean Sea. A few specics are found 
in Mexico and the United States. The genera found here are 
Helianthemum, Lechéa, and Hudsinia. 
XXXVIT 1. THE SUN ROSE. HELIA NTHEMUM. 
Tournefort. 
This genus contains a large number of beautiful species, much 
cultivated, delighting in dry and sunny situations, and therefore 
chosen, together with the Rock Rose, Cistus, to ornament rock- 
work, and plots in dry, sandy soils. The 2 exterior sepals are 
very small and bract-like, or wanting. The petals are 5, rarely 
3, sometimes none; the stigmas 3, large, fringed, more or less 
united into one. The capsule is triangular, 3-valved, with few 
or many seeds attached to central threads or on imperfect divi- 
sions projecting into the cell. 
