MACROSCOPIC STlttTTUBE. 1? 



.ortex also becomes rich in silica. As the vascular bundles 

 from the leaves bend inwards towards the interior of the 

 stem and then outwards, the isolated brown or black bundles 

 passing here and there through the wood afford a striking 

 characteristic of palmwood (Fig. 27). 



In Bamboos, numerous buds spring annually from under- 

 ground rhizomes and grow in a few weeks into tall leafy 

 shoots (culms). The size of the buds and consequently that of 

 the culms increases annually from the seedling stage, until for 

 a fixed term of years an even annual culm-diameter is attained. 

 When the culms blossom and fructify, the whole plant dies, 

 including the rhizomes. As in bamboos the pith of the buds 

 is segmented or chambered, when it extends into the culms 

 hollows occur separated by solid transverse walls at the nodes, 

 whence the culm-sheaths (modified leaves) spring (Fi. 2S). 

 The length of an internode, or the distance between the bases 

 of consecutive culm-sheaths, is therefore a measure of the 

 activity of the growth. The culm-sheaths soon fall, and tlu-ir 

 scars are visible externally as ring-like projections (nodes), 

 and at the axils of each sheath, or of the upper ones, leaf- 

 bearing branches spring from a depression in the culm. Owing 

 to their internal transverse walls, the culms are utili/able 

 for many purposes, while their lightness and extraordinary 

 strength add much to their utility ; their strength is largely 

 due to the large number of vascular bundles with scarcely 

 any vessels, that are crowded together near the periphery of 

 the culm with very little intervening parenchyma. 



A knowledge of the structural data of species of woods, as 

 well as their identification, is best secured by using three 

 sections made in different directions. The first of these 

 (Fig. 7, //), a cross or transverse section, is cut perpendicularly 

 to the pith or longitudinal axis of the wood : in this section 

 the medullary rays M, M appear cut through longitudinally, 

 the vessels (at a, e, </.) cut transversely in their width ; the 

 annual rings, owing to differences in adjacent structure, are 

 most distinct in this section. Hence most authors, who deal 

 with the identification of woods or the study of wood-structure, 

 show transverse sections only. Nordlinger * is the chief write 

 * II. NiinlliiiKcr, QnciBchnitte von loo Ilol/sirtcn, 1862, erweit* rt, 1883, mit 

 ILoixarteu /u 11 Biin<lcu."' 



C 



