132 



OF THE VEGETABLE CELL. 



649. WOOD CELLS, which are finally filled up by the repetitions of 

 the secondary layers, leaving only minute points of the original cell-wall 

 bare and transparent. 



658 



560 659 561 



Forms of cells. 560, Wood-cells. 561, Cellular tissue of a rootlet, etc. 



650. PITTED CELLS, a variety where larger transparent points appear, 

 surrounded by 2 or 3 rings (pine and the Coniferse in general). 



651. SPIRAL CELLS, where the secondary layer consists of spiral fibers 

 or bands. There may be a single fiber, or several (2 to 20) united 

 into a band. It is usually elastic and may be drawn out arid uncoiled. 



818 



562 563 565 



562, Polyhedral cells of parenchyma in pith of Elder. 563, Stellate cells in pith of Rush. 

 565, Spherical cells in Houseleek. 566, Wood-cells and ducts of Oak. 564, Wood-cells of 

 the Flax-fiber. 



These beautiful cells may be well seen in a shoot of elder, in the petiole 

 of rhubarb, Geranium, strawberry. In the two latter, if gently pulled 

 asunder, the coiled fibers appear to the naked eye. 



652. ANNULAR CELLS, wlien there are numerous rings within, instead 

 of a spiral coil, as in the stems of balsam and some Cryptogamia. 



653. SCALARIFORM CELLS, when the rings seem conjoined by bars 

 crossing between them, giving an appearance compared to a ladder 

 (scala), as in the vine and ferns. Porous cells with the secondary 

 layers full of perforations, reticulated cells, as if a net-work ; and many 

 other forms. 



