86 ON SOME CASES OF INVERSION, 
A common occurrence on the leaves of Yucca flaccida is the 
production of tubular horn-like processes from the margins. 
the central vascular bundles the arrangement is normal, but in 
those of the tubular portion the position of xylem and phloem is 
reversed, the phloem being nearest to the axis. 
REVERSED ARRANGEMENT OF THE PALISADE CELLS. 
at the base, so as to expose the dorsal surface to the light. The 
stomata are on the ventral surface in this case, but no change 
from the leaf, thus in the orange an outgrowth from the under 
surface is sometimes met with, having its ventral or green surface 
turned in the opposite direction from that of the rimary leaf, 
thus :-— fe) dark green surfaces, the thin lines 
paler surfaces. Occasionally in 
the Portugal Laurel (Dickson, Journal of Botany, 1867, 822) in 
REVERSED POSITION OF THE STOMATA. 
Although the stomata are by no means confined to the dorsal 
surface of the leaf, yet they occur there generally in greatest 
numbers. An exception may be noted in the cotyledons of many 
* Dickson, “ Foliage leaves of R ” : : 
part 1 (1885), t. ix,—xii, uscus,”” Trans, Bot, Soc, Edinb., yol. xvi. 
