LIBER. 



[ 387 ] 



LIBER 



(PI. 21. figs. 2, 3, 25). This does not appear 

 to depend upon the primary cell-wall, and 

 therefore cannot be taken as a proof of the 

 origin of the latter out of minute elementary 

 fibres (see Spiral Structures). 



The importance of liber as a material for 

 textile fabrics has been spoken of under Fi- 

 brous Substances, and examples cited; 

 figures of various kinds of liber-fibre are given 

 in Plate 21. A few particulars relating to the 

 stmcture and arrangement of liber may be 

 given here. 



In Dicotyledonous stems they are usually 

 placed in large bundles opposite to the fibro- 

 vascular bundles of the wood, as in Urtica, 

 Viscum, Clematis, Quercus, &c. ; sometimes 

 in small irregular groups, as in Vinca and 

 Limim ; in other cases they stand in single 

 rows, alternating with parenchyma {Cupres- 

 sinece and Taxinem), while in many plants 

 they are in-egularly scattered, as in Ehizo- 

 phora, Cinchona, Nerium, &c. Isolated liber- 

 eells occur on the pith of young shoots, and 

 may be readily seen in the elder, and Rhizo- 

 phora ; in the long woody radicles developed 

 from the seeds of the Rhizophoreaj, isolated 

 branched liber-fibres (PI. 39. fig. 31) occur 

 scattered throughout the whole mass. 



In the Monocotyledons they occur asso- 

 ciated with short wood-cells in the fibro- 

 vascular bundles, but they form alone the 

 fibrous bundles, often intermixed with and 

 prolonged fi'om the ends of these, occurring 

 especially in the outer part of the stem of 

 herbaceous Monocotyledons, such as Lilies 

 and Grasses, and in the fleshy cortical layer 

 of rhizomes, as in Sparganium, &c. 



In both famiUes they occur with the spiral 

 vessels and wood-cells in the ribs or veins of 

 leaves (as in Fhormium tenax), bracts, spathes 

 of Palms, &c. 



Liber-cells are generally drawn out very 

 gradually to a point at each end; sometimes 

 they are very long ; Schleiden states he has 

 seen them 5 ' or 6". Sometimes they exhibit 

 expansions at jiarticular points, as in the 

 Apocynacese commonly. The branched 

 forms in Rhizophorese, &c. are usually much 

 shorter than the simple fibres, and their 

 form is often very irregular (PI. 39. fig. 31). 

 The diameter varies a great deal in some 

 plants, and we should scarcely ventm-e to 

 say that the microscopic appearance of a 

 liber-fibre would suffice for the determination 

 of the natm'e of the material of any textile 

 fabric, beyond the distinction of cotton (or 

 vegetable hair) from linen or other liber, but 

 reagents affect them diff^erently. The ap- j 



pearance presented by many kinds of fibre 

 vmder the microscope, in the state in which 

 they occur in commerce and after treatment 

 with acids, is shown in PI. 21. figs. 2-7, 25 

 & 26. The figures are taken from very cha- 

 racteristic examples, but many modifications 

 occur in subordinate quantity. Flax {Linum 

 usitatissimum) (fig. 2) has the walls much 

 thickened mth distinct pores ; it exhibits a 

 very oblique, close striation after boiling 

 with nitric acid. Jute, the liber of Corchorus 

 capsiilaris, has thinner walls, with constric- 

 tions at intervals and blunter ends (fig. 3); no 

 spiral streaks come out here on boiling with 

 nitric acid. The fibre from the Cocoa-nut husk 

 occurs in bundles (fig. 4) ; when isolated or 

 boiled with acid, the walls are found thin, 

 with wiQle open spiral streaks (slits in the 

 secondary layers) ; the ends are blunt (fig. 5 

 a, b). The fibre of hemp {Cannabis sativa) 

 somewhat resembles flax, but is coarser and 

 becomes swollen up and brittle, readily 

 breaking across, when boiled with nitric 

 acid (fig. 6) ; no si)iral streaks. The liber- 

 fibres from the bundles of Musa textilis 

 (fig. 7) are fine and tough, and not much 

 altered by boiling. Those of Boahmeria nivea 

 (fig. 25) are coarse, rough on the outside, 

 swell up much and exhibit marked spiral 

 slits when boiled with acid, also very distinct 

 lamination of the thick wall (fig. 25 c). 

 Bahmeria Puya (fig. 26) closely resembles 

 the former, but the spiral striation is not 

 very evident, and the wall splits readily in 

 the longitudinal du'ection (fig. 26 c). The 

 spii'al striation is well seen in fig. 30 of 

 PI. 39, which represents the end of a liber- 

 fibre from Vinca minor after boiling with 

 nitric acid. 



All our observations on liber-fibres lead us 

 to believe that they are true elementary 

 organs ; but we doubt whether the milk-ves- 

 sels are always liber-fibres, as asserted by 

 Schacht, Further research is required. 



The liber bundles of bark are sometimes 

 set free as loose stringy fibres by the decay 

 of the outer parts of the bark, as in the vine. 

 Clematis, &c. In some plants they take a 

 wavy com'se, anastomosing laterally so as to 

 form connected reticulated sheaths over the 

 cambium: in thelimethese sheets, formed year 

 after year, may be detached by maceration, 

 and form bast, the material used for matting, 

 &c. In the Thyme L^ACE^ (lace-bark 

 trees) the annual layers of liber can be de- 

 tached from each other, and form sheets of 

 fibrous tissue, sometimes firm and tough, 

 sometimes almost as delicate as muslin. 



2c2 



