FIBRES. 



129 



The fibres in question are frequently called also Bast-fibres, or Bast-cells, after a 

 region in which they occur especially often in the Dicotyledons, and, in connec- 

 tion with these terms, Sanio has called those fibres which occur in the secondary 

 xylem, and which belong also in part to this category, bast-fibre-like, or libri/orm 

 fibres. Comp. Chap. XIV. P. Moldenhawer ^ calls them fibrous tubes. 



The name bast, or liber, is at present used for two quite different things. Originally it 

 was used as a topographic anatomical term, for a definite region of the cortex of the 

 Dicotyledonous stem, which is, it is true, as much characterised by definite forms of 

 tissue occurring in it as by its position (comp. Chap. XV), Among these forms of tissue 

 sclerenchymatous fibres are quite generally characteristic ; they are present indeed in 

 many cases in very large quantity, and are very conspicuous as compared with the other 

 tissues. On the latter ground, and since the really characteristic structure of this cortical 

 region was not known, they were considered as the essential tissue of the bast-region, and 

 the name bast was transferred from the region to the sort of tissue, but later again used 

 for both without sharp distinction. Since the sort of tissue is by no means limited to 

 this region, the result was that bast was found at other places than in the bast, or that there 

 is bast without bast, in other words that doubt and controversy arose. Now it is in itself 

 indifferent which meaning is attached to the name, and grounds may be brought forward 

 for authorising both the above uses of it, but it certainly cannot be used for two quite 

 different ideas. In the choice to be made accordingly it seems to me decisive that the 

 topographic meaning of the word is the older, and has always been the more usual. Its 

 use will therefore be here limited to the region to be treated of later, and the fibres in 

 question will therefore be called Bast-Jibres, wherever they belong to this region. 



The form of the sclerenchymatous fibres varies within the above stated limits ac- 

 cording to species and part. Their transverse section is acutely angular, where they 

 are closely united into bundles ; it is round in such fibres as lie single and loose in 

 intercellular spaces, as in many leathery leaves, in the foliage of many Aroidese, &c. 

 Those firmly connected into bundles are as a rule simple, i.e. unbranched, spindle- 

 shaped, usually with continued and gradual decrease of transverse section towards 

 the ends, while the much-elongated forms are usually drawn out at the ends into ex- 

 tremely fine points. This form — subject it is true to many exceptions — is the rule 

 also for the fibres occurring in longitudinally elongated parts, but not closely con- 

 nected into bundles : for instance, for most of the fibres, and even the isolated bast- 

 fibres, which are scattered in the parenchyma of the roots of many palms (Chamgedorea 

 elegans), the petioles and pinnae of Cycadese -, &c. A remarkable peculiarity of form 

 is shown by the very long bast-fibres of many Apocyneae, and Asclepiadeae (Nerium, 

 Vinca, Asclepias spec), since they are in their longitudinal course alternately nar- 

 rowly constricted, and then again suddenly distended; the same is the case, in 

 rather irregular form, in the bast-fibres of species of Sida, Urena, and the species of 

 Corchorus which yield Jute ^. 



Even the spindle-shaped fibres, which have just been mentioned as being 

 usually simple, show not uncommonly, when isolated, shortly- and unequally- 

 branched ends, or here and there at other points a branch usually of insignificant 

 size. 



' Beitr. pp. 11-61. ^ Moldenhawer, Beitr. p. 34. 



^ S. Wiesner, Microskop. Unters. p. 24 ff., and Idem, Rohstoffe, cap, 11, 



K 



