86 



4. In a number of trees, the bark exfoliates in definite layers (Fig. 1034), the separation being in 

 the zone of weakness, known as the separation layer, which is composed of loose and weak cells that alternate 

 with the denser and stronger cork layers (p. 709). [The figure above quoted is that of a Ribbony bark, 

 analogous to, e.g., E. viminalis, on a very reduced scale.] 



5. In trees with scaly bark, the cork layers separate into patches or arcs, as in the Sycamore (Acer 

 pseudo-platanus), Cherry (Primus Cerasus), and Pine (Pinus). [The bark of some Pines has a close 

 superficial resemblance to that of some of the Bloodwoods, e.g., E. corymbosa.] 



6. While in plants with ringed bark, the cork layers form concentric cylinders, and the bare shreds 

 or slivers off (as in the Grape, Vitis, and Arbor-vitae, Thuja). [I can find no useful Eucalyptus analogy 

 here.] 



7. In trees with shaggy bark the exfoliating masses are elongated, and in the birches the bark 

 exfoliates in thin papery layers (p. 709). [The Eucalyptus barks which approach nearest to those of the 

 Birches are those of some of the extreme members of the Lepidopkloias, such as E. miniata and 

 E. phoenicea, but the resemblance is not close.] 



4. VARIATION IN BARKS OF THE SAME SPECIES. 



This has been referred to by only a few authors. Following is an illustrative 

 reference : — ■ 



There are exceptions (to Mueller's cortical system), for instance to the Leiophlohe ; for 

 E. haemastoma, E. laligna, E. viminalis, E. stellulata, and E. punctata are somewhat half-barked, while 

 instances occur in which E. tereticornis has fibrous bark. The different kinds of Box are not always 

 half-barked, and so some of the Heniiphloite incline to the Leiophloife in extreme age. I have noticed 

 this peculiarity in E. largiflorens (bicolor) (he probably means the species afterwards known as 

 E. Bosistoana F.v.M., J.H.M.), and in some of the Blackbutts (E. vilularis) ... in the Woollybutt 

 (E. longifolia), of which the Baron (von Mueller) regards the bark as wrinkled, somewhat fibrous and 

 persistent, I have seen old trees which might have been mistaken for E. tereticornis, their trunks having 

 completely shed their bark, and become similar to Gum trees. . . . (Rev. Dr. Woolls in Proc. Linn. 

 Soc. N.S.W., xvi, 60, 1891.) 



While there is undoubted variation of bark in the same species, it is proper to 

 point out that it is also a fact that, some of the instances quoted by the older writers 

 are not to the point, because they were unconsciously including two or more species 

 under one name. I have in my mind's eye such cases as E. paniculata and E. fasciculosa 

 on the one hand, and E. sideroxylon and E. leucoxylon on the other. The first member 

 of each pair is an Ironbark, and the other a Gum, but, because of the similarities oi 

 herbarium material, each pair was looked upon as identical, until realisation of the fact 

 that their barks are totally distinct led to their final recognition as separate species. 

 Dr. Woolls' reference to E. tereticornis occasionally having " fibrous bark " probably 

 refers to E. exserta, and so on. 



The amount of rough bark at the base of a Gum is well shown in a photograph 

 of E. Benthami, to be reproduced later, where it will be seen that a certain specimen 

 could readily be grouped as a half-barked tree. The cause of the unusual amount of 

 rough bark is ringbarking. Such a condition is stimulated by violence in various 

 forms, e.g., cincturing, wounds, insect-action, and also by absence of shelter. Indeed 

 the description of a bark should only be made from a normal healthy tree. 



