264 M. WICHURA ON THE WINDING OP LEAVES. 



deficiency of transverse and an excess of longitudinal growth. 

 Winding leaves agree perfectly in this respect with winding 

 stems and tendrils, the thread- or string-like shape of which at 

 once reveals the predominance of longitudinal growth. 



§3. 



Another peculiarity of winding leaves might be sought in the 

 distribution of their stomates« In the ordinary, not winding 

 leaf, they are chiefly placed on the lower face, next the ground, 

 in order, as is supposed, to come, in this way, into immediate 

 and close contact with the gases and vapours ascending from 

 beneath. A differently contrived distribution of the stomates 

 should consequently be provided for winding leaves, which by 

 their curvature often change the relative position of their two 

 faces toward the vicinity. This conjecture finds a very striking 

 confirmation in the stem-leaves of the Alstrcemerm, which turn 

 quite over by a half-revolution, for, according to the beautiful 

 observations of Lindley, these bear the stomates, contrary to the 

 ordinary rule, on the upper face, turned towards the ground 

 only by the twisting. The winding leaves of the Grasses also, 

 as I have had an opportunity of observing, present anomalies, 

 in so far that they are furnished with stomates almost equally 

 on both sides of the leaf. Unfortunately I was unable to extend 

 these somewhat ^ time-devouring ' researches to other families. 

 I can therefore only offer a conjecture that winding leaves are 

 distinguished from those not winding by a more or less aberrant 

 distribution of the stomates. 



§4. 



In other respects, winding leaves present httle that is striking 

 in their external appearance. Not twining round a support like 

 winding stems, they complete their curvatures in the free air, 

 and from their slender, linear form, one is at first sight inclined 

 to ascribe their curvature to accidental effects of the wind and 

 of desiccation. The detection of the regularity prevailing in 

 their direction unfolds the error of the supposition, and opens 

 to our view a rich and everywhere ready field of observation, 

 where we previously passed by in indifference. 



