Delabeche, and many others, have already been borrowed from the 

 sister Science, this meed was justly due to one of the fathers of British 

 Geology, of whose friendship and obliging disposition I have myself 

 personally a lively recollection. 



Greenovia is distinguished from Sempervivum, and, indeed, from 

 all known Crassulace^:, by its deeply immersed ovaries, their anom- 

 alous placentation, and the position of the ovules, and the not less 

 unusual dehiscence of the fruit. Its habit is that of the true European 

 House-leeks, and not of the Canarian forms, Ionium, Aichryson, and 

 Petrophtes of the Phytographia. 



It is scarcely possible to avoid some error in describing dried speci- 

 mens of a family so difficult to examine in that state as the Crassula- 

 ceje. This will be the proper place to rectify one of these, and to men- 

 tion a new species of this Genus, till now confounded with the present 

 plant. The inspection of living plants of both, sent from the Canaries 

 with the dried collection in 1830, and preserved since by Mr. Young, 

 in his nursery at Milford, near Godalming, has enabled me to do this. 

 Mr. Yotjng, indeed, thinks that there is still a third species amongst 

 the living specimens sent ; but this cannot be so easily ascertained at 

 present. This new species I call Greenovia rupifraga, as it grows in 

 the fissures of naked tufa, which it widens by the increase of its stems. 

 Its leaves are wedge-shaped and narrow, instead of being rounded and 

 spathulate as in Greenovia aurea, with a much more prominent point 

 or tip, formed by the projecting midrib, and their sea-green colour is 

 much more silvery. A particular description will be given of this plant 

 whenever it flowers. 



The true Greenovia aurea inhabits the woody region on the rocks 

 called Los Organos, in the valley of Orotava, above Aqua Mansa, in 

 TenerifTe, and on Mount Saucillo in the Grand Canary, where it was 

 found by Despreaux. Greenovia rupifraga is found on that lofty 

 chain called the Filo de las Canyadas*, which forms the lips of the 

 great primaeval crater of the island, out of which the cone of the Peak 

 springs. Its station being thus above even the region of Pines, where 

 there is frost occasionally, it is very possible the species will sustain 

 the winters of England, if planted in a dry spot. Damp must be care- 

 fully guarded against, as the station which it inhabits being above the 

 clouds, is as arid as the great Sahara. On the contrary, the beautiful 

 zone of Laurels, on the outskirts of which the G. aurea is found, drips 

 with continual moisture from the clouds floating on the surface of the 

 trade winds, and which are arrested in their progress southwards by the 

 lofty mass of the island. 



It is probable that Christian Smith likewise confounded these two 

 species, for his habitat of Mount Chiquita belongs to the high region. 

 In the plate 36 of the Fhytographta Conarietms, the figures have, 

 unfortunately, been taken indiscriminately from both these plant*, 

 This confusion may be thus rectified, the figures 3, 5, (5, 7, 8, 8 bis, 9, 

 10, 11, and 12 belong to Greenovia aurea, the remainder, I, 2, 4, 13, 

 14, and 15, represent Greenovia rupifraga. P. B. Webb. 



* As the English printing offices do not possess the Spanish liquid n, I insert a 

 y for the pronunciation. 



Fig. 1. Two Pistils. 2. Section of an Ovary; — magnified. 



