78 



MOKPHOLOGY OF THE CELL. 



pass over into the variety shown in Fig. 59, No. 18. The latter 

 are known as " conjugate cells." 



PROSENCHYMA PROPER. 



256. Typical wood-cells. These are best illustrated by elon- 

 gated, often pointed cells, of which good examples are found in 

 the cambium layer (that is, the layer of merismatic or formative 





FIG 58. Drawings of wood-elements. 1-7. Avicennia sp. 1. Wood-parenchyma 

 cells united with each other; tangential section. 2,3,4. Conjugate wood-parenchyma 

 cells isolated by Schulze's solution. 5, 6. Portions of spirally striated libriform fibres 

 isolated by Schulze's solution. 7. The septum of a duct. 8-12. Tectoiia grandis; the 

 elements separated by maceration. 8. Conjugate wood-parenchyma cells. 9. Ordinary 

 wood-parenchyma fibre 10. Substitute fibre. 11. Simple libriform fibre. 12. Sep- 

 tate libriform fibre. 15. Porlieria hygrometrica ; conjugate substitute fibres seen in 

 radial section. The wood-cells are omitted in order not to confuse the diagram. 

 37. Radial section through the wood of Jatropha Manihot. 38. Tangential section 

 through a libriform fibre and two cells from a medullary ray of the same plant. 

 39-42. Bast-cells of Cytisus Laburnum. 39. Cross-section through a part of a young 

 bast-bundle acted on by chloroiodide of zinc. 40, 41, 42 Cross-sections through young 

 bast-cells, acted on by chloroiodide of zinc. (Sanio.) 



