THE FIB RO- VASCULAR SYSTEM. 



117 



146. The bundle of the adventitious root of Ranunculus 

 repens is very different from the one just described. It may 

 be briefly described as composed of a mass of tracheary tis- 



Fig. 106. Transverse section of hypocotyledonary portion of stem of Ricinus com- 

 mimis. r, r, parenchyma of the prinnry cortex ; w, parenchyma of the pith . b, 

 bast fibres ; y, y, soft, bast; c, cambium ; g, g, large pitted vessels ; t, t, smaller pit- 

 ted vessels ; cb, continuation of the cambium into the pan-nchjma lying between the 

 bundles the parenchyma-cells are repeatedly divided by tangential walls. Between 

 the primary cortex r and the fibrous tissue of the phloem lies a layer, the so-called 

 bundle-sheath, filled with compound starch grains. Highly magnified. After Sachs. 



sue, which is cross-shaped, as seen in transverse section (g, 

 r, g, Fig. 108), and four masses of sieve tissue, which lie in 

 the angles between the projecting portions of the traoheary 

 tissue. Around the whole is a layer of pericambium (p, 



