1^:8 SCLERENCHl'MA. 



S/cgma/a, and which, as shown by later investigations of Rosanoff', occur not un- 

 frequently among the IMonocotyledons also. They always appear on the outer 

 surface of sclerenchymatous or sclerotic bands of fibres (either such as pursue a 

 separate course, or accompany vascular bundles), and are applied to these in longi- 

 tudinal rows, which by the arrangement of their elements lead us to conclude that 

 they arose by transverse division of spindle-shaped cells. The single elements are 

 small, and have the form of flat, or (in the Monocotyledons) plano-convex, usually 

 rectangular plates, with the flat side contiguous with the fibrous band. As regards 

 their structure they are characterised by unequal thickening on different sides, 

 usually also by partial silicification of their walls ; they vary extremely in individual 

 cases according to the species or systematic group. In the species of Trichomanes, 

 the wall is strongly thickened on one side, i. e. on the inner face, which is contiguous 

 with the fibrous band. In some few species the thickening is uniform on this surface; 

 it is equally rare to find it so arranged that it occupies the peripheiy of the inner 

 wall in a ring-like manner. Usually there rises from the middle of the inner wall 

 into the cavity a cushion-like protuberance, hollowed in the middle, or comb-like 

 bands placed symmetrically near the middle. On the varying special forms of these 

 outgrowths, compare /. c. Those outgrowths protruding' inwards and the region 

 immediately surrounding them are distinguished from the rest of the wall, which 

 shows the cellulose reaction, by their granular appearance and strong silicification. 



Similar covering plates, perhaps more properly included under the crystal- 

 containing structures, since each contains an aggregation of calcium oxalate, occur, 

 according to a short statement by Mettenius, in certain of the Cyatheaceoe. 



The fibrous bands in the stems, leaves, and roots of Orchidese (Pholidota, 

 Stanhopea, &c. ^), Palms (Chamaerops, Phoenix, Caryota, &c.), of Maranta compressa, 

 Arundinaria spathiflora, have interrupted longitudinal rows of plano-convex stegmata 

 on their exterior. The convex outer wall of these is thin, the inner thickened 

 to a half-spherical rough body, which almost fills the cavity, and consists mostly of 

 compounds of silicon. Often 2-3 such silicified bodies occur in place of one. 

 (Rosanoff found similar silicified bodies also in cells containing chlorophyll and 

 starch on the fibrous bands in the margin of the leaf of Galipea macrophylla, one of 

 the family of Diosmese.) The fibrous bands in the lamina of the leaf of Scita- 

 mineaj (species of INIaranta, Heliconia, Thalia) show small stegmata, the structure of 

 which seems to differ from that just described, and remains to be investigated. 



Sect. 30. Selerenchymatous fibres, of elongated spindle-like shape, with 

 sharp ends, simple or branched, are the form of strengthening tissue which is 

 universal, especially in Phanerogams ; they are sometimes in uninterrupted lateral 

 connection, and united, with pectinated * ends, into bundles and sheaths ; sometimes 

 they are imbedded singly in other tissues. 



' Botan. Zeitg. 1871, p. 749. 



^ Compare Link, Botan. Zeitg. 1849, P- 75°* 



^ [It is believed that this translation will convey the meaning intended by the use of the word 

 ' verschrankt,' the idea being that of an arrangement similar to the fingers of two folded hands, or of 

 two combs {pcctefi) with the teeth of the one passing between those of the other. The word 

 pcctinatory will be used subsequently in describing the course of the vascular bundles (Chap. 

 VIII, A).] 



