202 M. B. WELCH AND A r R. PENFOLD. 



under wliich the two species grow are taken into consider- 

 ation. 



It will be seen from the transverse section of the two 

 species that the palisade layers in B. pinnata show much 

 greater development, while the intercellular spaces in the 

 spongy mesophyll are much smaller than in B. thujona. 

 These characteristics are typical in the former species of a 

 heliophilous plant, whereas in the latter species we have a 

 distinctly sciophilous type. Warming (Plant Ecology) says 

 that the stomata of sciophylls are found on either surface 

 of the leaf, w r hereasin dorsiventral heliophylls the stomata 

 are confined to the lower surface, or are more numerous 

 there than on the upper face. In the case of B. pinnata 

 and B. thujona, however, this generalisation is to some 

 extent reversed, since stomata are very rarely found on the 

 upper surface (Bundanoon), and were confined to the lower 

 surface only, in material examined of B. thujona from 

 Narrabeen. In B. pinnata, however, though somewhat 

 smaller and fewer on the upper surface than on the lower, 

 they are, nevertheless, quite numerous. IB. thujona^ 

 possesses also a lower epidermis with very sinuous lateral 

 walls, a feature scarcely found in B. pinnata. In the case 

 of B. thujona, the style is usually much longer and thinner 

 than the stigma more dilated than in B. pinnata, with its 

 short thick style. The flowers are larger in the former 

 species than those of B. pinnata, and usually paler in colour. 



Hooker mentions the fact that the leaves of B. Gunnii 

 smell " powerfully of rue and tansy," but B. thujona is 

 apparently a much more robust plant, attaining a height 

 of 8 — 12 feet, whereas the Tasmanian plant grows to 2-4 

 feet in height. The stigma of B. thujona is also much less 

 capitate than is figured by Hooker under his species in- 

 Flora Tasmania, Vol. i, 1. 10; in B. thujona also the leaves 

 are as a rule decidedly serrulate, whilst no mention is made 



