2,9% 



PRIMARY ARRANGEMENT OF' TISSUES. 



pass on further in the middle, sometimes at the periphery of the pith, and some 

 insert themselves at an acute angle on similar branches from lower leaves, others end 

 blind. At the foliar gap the bundles, which are themselves about as thick as a 

 bristle, are surrounded by brown sclererichyma, or supported by it on one side, and 

 these sheaths of sclerenchyma, which are closed or open on one side, accompany the 

 bundles for a long distance downwards ; sometimes they also anastomose with 



s' U 



Fig. 139. — Cyathea Imrayana; 

 natural size. From a dead stem, the 

 soft parts of which had rotted away ; 

 the stem is halved loBgitudinally, 

 and seen from within, " The figure 

 ihows a piece of the tube of vascu- 

 lar bundles with one foliar gap, l—l, 

 and a leaf-scar exactly halved longi- 

 tfidinally. Prom this the bundles of 

 sclerenchyma which accompany the 

 vascular bundles "may be seeii to 

 branch off, and from there those 

 which accompany the medullary 

 bundles arise as branches and pass 

 down into the pith with many 

 branchings and anastomoses ; some 

 of them'have blind pointed endings; 

 the one which extends furthest 

 downwards has anastomosed -with 

 one Cbmingfrom alowerleaf. Ofthe 

 bundles which end at the leaf-scaf; 

 ill originates frpm the pith, the rest 

 frwn the maf-gin bf thij foliar gap. 



Fig. 140.— Cyathea Imrayana; axile longitudinal section through 

 the same stem as Figs. 141 and 142 ; natural size. The section is about ' 

 3mm. thick, and for the most part transparent; the black bands of 

 ' sclerenchyma and j^ff/e vascular bundles here represented in one plane 

 do not alMie exactly in this plane, but are all near it. Certain parts of 

 the chief sclerenchyma^dus-sheath ,f — y wHich show through, and at 

 the bottom two portions ofthe surface of the stem seen obliquely, are 

 shaded off as they pass from the surface of section. The letters a, s, 

 y,/'have the same meaning as in Fig. 141; r corticaf bundles, i leaf- 

 scars, bl vascular bundles parsing out mto leaves, lu insertions of roots, 

 ni a foliar bundle' running info"lhe pith; above x blind ending of a 

 medullary bundle (examined under the microscope). 



similar sheaths, which descpnd from leaves side by side with or below them,, some- 

 times they diminish downwards and end blindly in a point, while the vascular bundles 

 continue their downward course alone beyond these endings (comp. Fig. 140)- 



