B72 



MANUAL OF BOTAKY 



can be observed at its lower part, but as the axis is examined 

 higher up, the cylinder is found to break up into as many strands 

 as there are vascular bundles, and these separate from each 

 other, each becoming clothed with its own pericycle and endo- 

 dermis, continuous below with those of the original monostele. 

 The separate bundles may be .scattered through the substance 



FlO; 757. 



Fig, 758 



Fiij. 757. Diagram of stem in two 

 species of Equisetum. A. E. 

 limosum, n. The separate 

 bundles or schizosteles, eacli 

 with its pndodermis. B E. 

 hienuile. The schizosteles, s, 

 have tlieir endodermis fused 

 laterally. In hoth figures I = 

 cortical lacunse. After Pfitzer. 

 Fig. 758. Section of vascular 

 bundle of Equisetum limosum. 

 ert. Endodermis. pe. Pericycle. 

 X. Xylem. ph. Phloem. I. La- 

 cuna. After Dippel. 



of the stem, or may be arranged in a circle. At intervals they 

 anastomose with each other, forming a network of bundles. 

 This is due to a. varying and irregular differentiation of the 

 tissue of the plerome. 



This type of arrangement is rare among flowering plants, but 

 it is not uncommon among the Cryptogams, being very frequently 



