838 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XX. 



including here and there large pitted vessels, with very little 

 wood-parenchyma (Fig. 1). One cannot help' observing here the 

 marked resemblance, this secondary wood bears in general to the 

 secondary wood of the Coniferae most of which are xerophytic. 

 The wood fibres of this plant show (in transverse and longitudinal 

 sections) a definite cavity, so that we have here a tissue made up 

 of numerous closed capillary tubes. This peculiarity of the wood 

 is itself a special adaptation to conserve large quantities of water 

 in the body of the plant, and at the same time affords facilities to 

 the transport of the cell-sap or watery solution towards the leaf. 

 How the cell-sap travels through the root and stem and arrives at 

 the leaves is not the question at issue. The transport of cell-sap 

 through lofty woody stems is one of the ill-solved problems of 

 vegetable physiology. Opening that question here in connection 

 with the phenomenon to be explained would avail us nothing. 



A concomittant feature resulting from this abundance of wood- 

 fibres thus closely packed, and lessening of the wood-parenchyma 

 is the great reduction of the intercellular space system in the body 

 of the plant. The effect of it is that very little quantity of water 

 must be evaporating internally. 



The microscopic structure of a sufficiently grown older branch 

 which may be taken as the type of the structure obtaining in all 

 parts of the grown stem of any width, presents, in addition, still 

 further special features. The wood goes on increasing under the 

 action of the vital region. Cambium in rings, and is formed, as 

 before, of abundance of closely-packed wood-fibres with fitted walls 

 and of numerous fitted vessels comparatively of small diameter 

 (fig. 2). The wonder is not that there are so many pitted vessels 

 of the ordinary kind, but the wonder is that there are not more of 

 these. The most important special structural feature of the stem, 

 as it advances in age, is the formation in it by the Cambium in a 

 regular order of the large calibred ducts or conduits filled with phloem 

 tissue called the Interxylem Phloem. The phlcem tissue is made 

 up of sieve-tubes and phloem parenchyma and contains large quan- 

 tities of cell-sap (Fig. 3). These conducts of inter-xylem phloem 

 are not running as continuous tubes in their longitudinal extent, 

 but are short tubes interrupted at both ends and placed one over the 



