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 lasting, 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. The 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 line 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 CistdcecB are mostly confined to the temperate regions of 

 the northern hemisphere, and abound especially in the comitries 

 bordering on the Mediterranean Sea. A few species are found 

 in Mexico and the United States. The genera found here are 

 Helianthemum, Lechea, and Hudsonia. 



XXXVII. 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, Cistas, 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. 



