448 SAXIFRAGE TRIBE; HYDRANGEA. 



celled. The styles are commonly distinct, but are sometimes 

 adherent ; in the greater number of the tribe there are no more 

 than two, indicating that the ovarium is made up of but two 

 carpels. Each cell contains a large number of minute ovules. 

 The fruit is ordinarily enclosed in the calyx, and opens only at 

 the point. There is one genus, however, in which there is no 

 adhesion between the calyx and ovarium ; and there are several 

 in which the adhesion does not extend far up. In habit this 

 tribe a good deal resembles some of the Rosacese. 



616. The plants of this order are almost universally diffused 

 over the globe ; but they cannot be said to be of any direct 

 utility to Man. The name of the principal genus, Saxifrage, 

 however, is probably derived from the power which may be 

 attributed to the plants composing it, of breaking up the surface 

 of the rocks on which they grow, by insinuating their roots into 

 crevices, and afterwards causing them to distend in the same 

 manner as the Cacteae have been just now stated to do (. 610). 

 If this idea be correct, it is obvious that their function, in pre- 

 paring the surface of barren rocks and mountain sides, for the 

 habitation of plants of a higher order, is one of the most import- 

 ant in the whole economy of nature. At least twenty species 

 of this genus alone exist in Britain ; and some or other of them 

 are found in almost every rocky or exposed situation. To this 

 order belongs the very singular genus Parnassia (so named 

 because it is said to abound on Mount Parnassus), the British 

 species of which is the companion of the Sun-dew in its marshy 

 haunts, and rivals it in singularity of structure. In the latter, 

 the peculiar glandular hairs are found only on the leaves ; but 

 in the Parnassia they exist on the flowers. Alternating with 

 the stamens, there are five fleshy scales, divided at their edge 

 into numerous rays, each of which is tipped with a beautiful 

 pellucid greenish gland ; so that the flower, when viewed from 

 above, appears set with sparkling jewels. The Hydrangeas, 

 (which are not natives of Britain, but have been introduced 

 from China and Japan,) are also marsh plants, and should be 

 kept well supplied with water, when grown in gardens. A full- 

 sized plant requires as much as from 10 to 12 gallons daily in 



