THE VEGETABLE CELL 



15 



Fig IS 



Ctll iiom lh„ 

 mm « t 



cells of the cortical layer in Sphagnum, tlie liairs in the Cactaeea^, 

 particular layervS of the seed-coat in Gasimrina^ Salvia, many Po- 

 lemoniacese, &c, and in many plants to the anther-celk. Paiti- 

 cular organs composed of such :&brous cells, not unfie- 

 quently possess a spongy, soft consistence, e g., the 

 outer rind of the root of many tropical Oichidaceas and 

 Aroideae, the sepals of lUecebrum vertidllatum, the 

 pericarp of Oachrys Morisom, (7. odontalgica, the ribs 

 of the fruit of (Etimsd Oynapium. 



The annular jBbre (% 19) which runs in a trans- 

 verse direction on the cell-wall, crossing the longitu- 

 dinal axis of the cell at right angles, is to be regaided 

 as a slight modification of the spiral fibre. It not un- 

 frequently occurs alternating with the spiral fibres in 

 the same cells as the latter, e g., in the cells of many 

 anthers, in the sporangium of the Jungermannise, and 

 in the leaves o? Spliagmim, It may be regarded as a 

 middle form between the right and left wound spiral 

 fibres 



The reticulated structure of the secondary mem- ]J^f^^l 

 branes occurs infinitely more frequently than the regu- 

 lar spiral formation, and scarcely a plant can be found, 

 from the Mosses upward, in which this structure cannot be more 

 or less clearly distinguished in the majority of its cells. Some- 

 tunes, but in comparatively rare cases, the secondaiy membranes 

 of the reticulated cell resembles those of the spiral- 

 fibrous cell, in that they are likewise divided by closely Fi<j 19 

 adjacent pits into narrow fibres, which fibres, however, 

 do not run in a spiral direction, but are connected into 

 a more or less regulovr net, with nariower or wider, 

 roundish or angular meshes, e. r/., in the cells of the 

 wing of the seed in Swietema, of the poiicaip of Pi- 

 crichuon tingitanwm, P.vulgare, in the seed- coat of 

 Oucurhita Pepo, of the parenchyma of the leaf of Scmse- 

 viera gwineensis (fig. 20), in isolated cells of the pith 

 of Rubus odoTatue, ETythrina Oorallodendron. But 

 in the great majority of cases the secondary membrane 

 is perforated by comparatively small orifices at few 

 points only, and therefore does not appear under the 

 form of a net-woik of narrow fibres, but as a connected 

 membrane perforated like a sieve. Since this is the 

 usual condition, which occurs in almost all cells (see spovlhgmnrQf: 

 fig. 7), it will be unnecessary to cite examples ; yet pofmorpkl 

 it may be permitted to name some particularly charac- 

 teiistic cases, the investigation of which prepares the way to a com- 

 prehension of less distmct stiuctures, e.g., the parenchymatous cells 

 of the leaf-stalk of Gycas revolnta^ the thick walled pith-cells of 

 Hoya cmmosa (fig. 12), the cells which foim the stony concie- 





Cells from, tlie 



