FIBROUS CELLS. 45 
ance of a perforated membrane, and thus giving rise to the pitted 
cells just described), forms delicate threads or bands of vary- 
ing thickness -called fibres, which assume a more or less spiral 
direction upon its inner surface (figs. 87-89), and thus give rise 
to what are called fibrous cells. Such cells occur in various plants 
and parts of plants ; thus in the leaves of Sphagnum, the hairs 
of many Cacti and other plants, in the integuments of some 
} 
Fie. 85. Fic. 86. 
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Fig. 84. Cells with bordered pits or disc-hearing wood-cells of the Pine, 
with a double row of discs, which are on the same level, or opposite to 
each other, After Nicol.—RFig. 85. Cells with bordered pits or disc- 
bearing wood-cells of Araucaria excelsa, with double rows of discs, which 
are alternate with each other.—Fig. 86. Cells with bordered pits or 
disc-bearing wood-cells of Araucaria, with double and triple rows of 
alternate discs. After Nicol. 
seeds and fruits, as those of Salvia (fig. 152), Cobeea scandens, 
and Collomia, inthe spore-cases of certain Flowerless plants, 
in the inner lining of all anthers, in the root-sheath of the aerial 
roots of many Orchids, and in several other instances. 
These fibrous cells also present some differences of appear- 
ance as regards the distribution of their fibres. Thus, in some 
cells the fibre forms an uninterrupted spiral from one end to the 
Fic. 87. Fie. 88. Fie. 89. Fie. 90. Fie. 91. 
Fig. 87. Spiral cell Fig. 88. Annular cell.— Fig. 89. Reticulated cells. 
— Fig. 90. Pitted and reticulated cell.—— Fig. 91. Wood-cells of the Yew 
(Taxus baccata), After Mohl, 
other (figs. 87 and 152): such are termed spiral cells. In other 
cases the fibre is interrupted at various points, and assumes the 
form of rings upon the inner surface of the cell-wall (fig. 88), 
and hence such cells are called annular, Instances also occur 
even more frequently, in which the fibres are so distributed as 
