Instances of differences are given, and it is added : — 



Hundreds of trees and shrubs might be mentioned in which there is a distinct difference between 

 the foliage of the suckers and of the normal branches of the crown. (Kerner and Oliver, ii, 515-6.) 



Nor has the description of species and varieties from suckers or seedling 

 leaves been confined to writers on Eucalyptus : — 



Gardeners and descriptive botanists have frequently determined and described mutilated plants as 

 other species, hybrids, or varieties. They are neither the one nor the other. The peculiar appearance of 

 the altered members, resulting from mutilation, is exactly determined beforehand in each species; it is due 

 to the specific constitution of the species, and thus is part of its being. It is not produced by the external 

 influences which lead to the formation of the varieties, but is brought about by inherent necessity quite 

 independent of the influence of climate and soil. (Op. cit., ii, 518.) 



Practically all the researches on the anatomy of Eucalyptus leaves have been 

 made on those of the readily available E. globulus, in which species both sucker and 

 mature leaves are readily available. The most complete research is the masterly 

 paper of G. Briosi.* See also a study by H. Pocklington.f 



Then Henslow:]; says : — 



The chief differences 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§ speaks of the sucker ("dorsi ventral") 

 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. 8. 



(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 obtaining seed from certain interesting forms. Mueller's JEuoalyptograpliici and 

 Lubbock's " A contribution to our knowledge of seedlings," form the basis of our 

 present available information on the subject. 



Other characters of Eucalyptus leaves we require to knoAV more about are 

 their size, texture, and prominence of venation. They are minor characters, and 

 some species present much variation in this respect. 



* Ricerche intorno all'anatomia delle foglie dell' Eucalyptus globulus. 23 pi., Mi/ano, 1892. 



t The Microscope in Pharmacy; Eucalyptus globulus. Pharm. J own. (3), iii, 930; iv, 549. A„ useful 

 histological study of bark, leaves, &c. 



X Origin of Plant Structures, p. 63 (note). His "horizontal" are sucker leaves, and "pendulous" the mature 

 foliage. 



§ Structure of Eucalyptus globulus leaves. Journal of Pharmacology, iv, 169. Pharm. Journ., 28th Aug., 1S97. 

 p. 191. 



