132 



OF THE VEGETABLE CEIL. 



649. Wood cells, which are finally filled up by the repetitions of 

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

 bare and transparent. 



560 559 861 



Forma of cells. 560, 'Wood-oelle. 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 and uncoiled, 



5»1 666 



662, Polyhedral cells of parenchyma in pith of Elder. 66S, Stellate cells in pith of Bnsh. 

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

 the Flax-flber. 



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, when there are numerous rings within, instead 

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



653. SoALARiFORM cells, whcu the rings seem conjoined by bars 

 crossing between them, giving aii 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 

 -odier forms. 



