419 



CLADODIA. 

 (a) Economic {vide Chemistry). 



(b) Anatomy. 



Figures 271 and 272, taken through the median bundle and low down, 

 give some idea of the general structure in that portion of these organs. 



In Figures 273-274, the central vascular cylinder is seen to be divided 

 into several bundles, surrounded and separated indi\ddually by parench\Tnatous 

 cells, which also enclose between them and the phloem a comparative large number 

 of sclerench\-ma cells, which, in some cases, quite surround the lateral bundles. 



The fundamental tissue consists of sponge" and palisade mesophyll, and 

 large parench\Tnatous cells; the former, as obtains in normal leaves, predominating 

 in amount ; through this and equi-distant from each surface at f airl}- regular intervals 

 are bundles, and often accompanying these are oil ca\-ities surrounded by streng- 

 thening and secretionar\" cells or cavities, as in the case of that of the median 

 bundle. The epidermis is characterised bv a verv thick cuticle or outer wall, 

 whilst hypodermal cells are not often found. The palisade layer extends around 

 the whole phyllode, supported inwardly by the spongy mesophyll, intermixed 

 ^^dth large intercellular water or air ca^'ities. Stomata occur irregularlv scattered 

 on both surfaces. The sections illustrated were taken at various distances in 

 the cladodia. Figures 271-280.) 



Masters in "Linn. Soc. Trans.," ^'ol. XXI, Xo. 205, p. 7, states — "The 

 leaves have small resin canals close to the exoderm on the lower surface of the 

 leaf 'P. alpiiius^, and a single bundle." Speaking of the phvUoclade of P. alpinus 

 he states that — " beneath the upper epidermis is a layer of perfect parenchyma, 

 traversed b}- a central and by numerous lateral fibro-vascular bundles." From 

 the illustrations here given it is seen that similar characters occur in the 

 Tasmanian Phyllocladiis . 



Chemistry of the Leaf ^Cladodey Oil. 



Theoretical. 



The oil from this portion of the tree is of particular interest, because it 

 contains the only solid cr\-stallisable diterpene so far known. The principal con- 

 stituent of the o'l is pinene, which is Ijevo-rotatory, although the rotation is not 

 very high, and it appears to be the only CmHie substance present. Practically 

 pure pinene can be obtained in quantity from the cladodia oil of this species by 

 fractional distillation alone. The only other constitutent of importance in 

 the oil, besides the diterpene, is probablv a sesquiterpene, but o\\ing to the 

 presence of the sohd body it was difficult to separate by distillation, so that 

 it was onh" possible to obtain a small quantity of it, and its chemistry 

 could not be completed; some results, however, are recorded below. 



