468 



Fr. J. Mathiesen. 



are seen in В (26 such clefts — most of them larger — occur- 

 red in the root figured) by which all the phloem-tissue of 

 secondary formation is split into a corresponding number of 



radii, which in their 

 ^ outermost parts ap- 

 pear to be some- 

 what crumpled to- 

 gether, evidently by 

 pressure of the tis- 

 sue later on formed 

 by the cambium. In 

 these radii the 

 groups of sieve- 

 tubes are flanked 

 on both sides by 

 parenchyma. With- 

 in the cambium 

 some groups of ves- 

 sels are seen; cor- 

 responding to each 

 ray of tissue in the 

 cortex 1 or 2 rays 

 of groups of vessels 

 occur in the xylem, 

 divided reciprocally 

 by broad radii of 



parenchyma, in 

 which the clefts 

 from the phloem may be continued, and may reach almost 

 to the centre of the root. 



The portion of the stem with elongated internodes shows 

 a thin-walled epidermis with stomata; the cortex is few- 

 layered, and its cells contain chlorophyll-grains. When the 



Fig. 38. Pedicularis hirsuta. 

 A, Transverse section of the outermost layers 

 of the cortex of the root. B, Transverse sec- 

 tion of a portion of the stele of the root. 

 (Greenland.) (A and В about ^^д.) 



