256 REV. G. HENSLOW ON THE ORIGIN OF PLANT-STRUCTURES 
plante rejette comme une substance d’évacuation, tandis qu’elle 
doit retenir autant que possible l’eau de sa seve, lorsqu’il s’agit 
de prolonger la durée de ces fonctions vitales. Un role de 
certaine importance pourrait également revenir au phénoméne 
de réfrigération produit par l’évaporation, au moment du passage 
rapide des huiles éthérées & l’état de vapeur, phénoméne qui 
réagit contre la température communiquée par linsolation aux 
feuilles, dont le degré de chaleur détermine aussi la marche de 
Vévaporation” *. 
Mount Sinai appears to show like characteristic features of 
desert plants to a considerable height, viz. 7035 ft.; for Mr. R. 
M. Redhead, in some notes upon the flora, remarks t :—“ During 
our ascent of Gebel Masa, followed by that of Ras-es-Sifsafeh, 
two points especially struck me,—first the great preponderance 
of scented and especially Labiate plants ; and, secondly, the very 
woolly, tomentose character of those not labiated.” He also 
speaks of “a very fragrant Tanacetum or Artemisia with pinnated 
downy leaves.... Satureja montana and S. Juliana, I think, 
have an odour greatly resembling the incense used by the Greek 
Church, and are gathered by the monks for some ecclesiastical 
purpose. Salvia clandestina has woolly pinnatifid leaves.” 
This last mentioned species of Salvia is a most variable one, and 
has given rise to much discussion and nomenclature. If, how- 
ever, the effect of the environment be kept in view, which causes 
the variations, I think the passage from the European S. Verbe- 
naca with large flowers and glabrous leaves to the S. European 
and Desert forms will be probably found to be exemplified by 
a gradual reduction of the leaf so as to become more deeply 
indented or of the “coronipifolioid” type, by the glabrous 
surface passing through a pilose condition till it becomes tomen- 
tose as described by Mr. Redhead; while the flower, adapted to 
insects, runs through the usual degradations till it becomes cleisto- 
gamous. Bentham thus speaks of S. controversa, which S. clan- 
destina connects with S. Verbenaca t :—“ It appears that in the 
ordinary clandestine state of this plant the corolla is abortive, as 
frequently occurs in S. Verbenaca and S. clandestina, especially 
in their more southern stations.” 
* Vég. du Globe, i. p. 628. 
+ “ Notes on the Flora of the Desert of Sinai,” Journ. Linn. Soc., Bot. ix. 
p. 208. 
} Labiat. Gen. et Sp. p. 719. 
