MICROSCOPIC OBJECTS. 36 



Fig. 71. Transverse Section of Malacca Pepper Stem 

 (Piper nigrum), x 40. 



The section of this stem has been taken the better to illus- 

 trate some of the remarks made in the description of fig. 59. 

 Being a section of an exogenous stem, it has the central 

 cellular pith, the medullary rays proceeding from the pith to 

 the bark or outer skin, and also rays of the ordinary prosen- 

 chymatous or woody tissue. The five larger holes are trans- 

 verse sections of the ducts. 



Fig. 72. Transverse Section of the Stem of the Cocoa-nut 

 Palm (Cocos nucifera) , x 20. Endogen. 



Endogenous plants may be distinguished from Exogens by 

 their stems being destitute of medullary cells and concentric 

 layers of annual woody growth, also by their stems being 

 almost composed of cellular tissue although in some plants 

 the vascular tissue is largely represented, as, for instance, in 

 this Palm, the oval parts in the drawing representing the 

 vascular tissue seated in a mass of parenchymatous cells. 

 The large dotted ducts which are generally found in the 

 exogenous woods are also absent. Many Endogens are met 

 with in which the centre of the stem is entirely absent, as in 

 the Grasses &c. 



This section is best seen mounted in fluid. 



