IS EUCALYPTUS VAKIABLE 1 325 



Then Henslow 1 says: — "The chief difference between 

 the two forms of leaves I find to be as follows : — In the 

 horizontal leaf the upper epidermis is composed of small 

 cells, and there are no stomata. There is a palisade tissue 

 of one layer of cells, with lax mesophyll below the lower 

 epidermis. This latter has larger cells than the upper and 

 is provided with stomata. The pendulous leaf is a good 

 deal thicker than the horizontal. Both epidermides are 

 provided with a very dense cuticle in which the stomata 

 are deep-seated. There are four rows of palisade cells on 

 both sides with a chlorophyllous mesophyll between them. 

 The petiole is flattened so that the leaf can swing much in 

 the same way as that of the Poplar." 



A useful paper by Dr. Albert Schneider 2 speaks of the 

 sucker ("dorsiventral") leaves with palisade cells on the 

 upper side and stomata on the under side only. The mature 

 leaves " isolateral leaves or phyllodes " take a vertical 

 position with the convex edge directed upward. The 

 epidermis is alike on both sides. It will be observed that 

 his results do not agree with those of Henslow, — evidence 

 of variation. 



The anatomical characters of the leaves of Eucalyptus 

 offer, however, much room for research. See "stomata" 

 p. 327. 



(b) Cotyledon leaves — The shape of the cotyledon leaves 

 we know less about, and data are being collected. The 

 work has been hindered because of the difficulty of obtain- 

 ing seed from certain interesting forms. Mueller's Euca- 

 lyptographia and Lubbock's "A contribution to our know- 

 ledge of seedlings," form the basis of our present available 

 information on the subject. 



1 Origin of Plant Structures, p. 68 (note). His "horizontal"" are 

 sucker leaves and "pendulous " the mature foliage. 



2 Structure of Eucalyptus globulus leaves. Journal of Pharmacology, iv., 

 169 ; Pharm. Journ. 28th Aug. 1897, p. 191. 



