Rosti ceæ. 



51 



of the root. The secondary cortex consists chiefly of paren- 

 chyma. It shows concentric layers which result from circles 

 of sieve-tube-groups, the cambium for each circle of such 

 groups producing about 10 layers of parenchyma. Fig. 20, B 

 shows a group of sieve-tubes just outside the cambium, while 

 Fig. 20, C illustrates two such tubes from about the middle 

 of the cortex. 



In the rhizome, as in the food-storing root, a conti- 

 nuous cambium develops chiefly parenchyma. The periderm 

 in correlation with the short duration of life is not very thick. 

 An endodermis is present. 



The horizontal portions of the floral shoots are some- 

 what flattened. The 



nc 



activity of the cam- 

 bium is slight, and 

 the few groups of 

 vessels always re- 

 main separated by 

 primary medullary 

 rays. The two- 

 layered pericycle is 

 transformed to bast 

 which becomessome- 



Fig. 20. Potentilla anserina. 



.4, Fragment of a transverse section of a food-storing root taken 

 in the autumn ( M i); cc, central cylinder with groups of vessels ; 

 cb, cambium ; sr, secondary cortex ; pc, fragments of the dead 

 primary cortex; it. cork; /, concentric circles in the secon- 



what Stronger in the dary cortex with groups of sieve-tubes. B. A group of Bieve- 

 , . , . tubes just outside the cambium. C, Groups of sieve-tubes 



peduncle than 111 the f,.^ about the m jddle of the secondary cortex. B, C 



horizontal part. An about mfl - 



endodermis-like layer is present 1 . Within the epidermis 

 there is a layer of weak collenchyma. The stomata projed 

 above the level of the surface. 



The leaf varies considerably in size being from about 

 one-third of a metre (f. grandis Lehm.) to 3 — 4 cm. in length, 

 the hair-covering is also very different: in /. sericea Hayne, 



1 Cf. Edmund Orth : Beitr. z. Anatomie d. Gattung. Potentilla. 

 Dissert. Hamburg. 1893, p. 27. 



4* 



