Primulaceae. 



205 



В and С show similar sections of the cortex and cen- 

 tral cylinder, respectively, of a stem, where the rosette 

 has been more densely leaved. Both have this in com- 

 mon, that the inner layers of the cortical parenchyma 

 perish fairly quickly, except the endodermis which by divi- 

 sion of its radial walls keeps pace with the growth of the 

 central cylinder. The outer layers of the cortex acquire 

 thickened and lignified walls, thus forming! a continous 



Fig. 21. Androsaces chamaejasme. 

 A, transverse section of a stem, which has borne a few-leaved rosette. В and C, respec- 

 tively, the outer layers of the cortex with epidermis attached, and the centralcylinder with 

 the endodermis of a stem with many-leaved rosette. (J^, £ and C, obj.8, oc. 4.) (Jugor Schar.) 



sclerenchymatic ring. By comparing fig. 21, A with fig. 21, В 

 it is apparent, that the thickness of this ring differs in 

 the two types of shoots; in B, 5 — 6 layers take part in 

 the forming of the stereome, while in A, this only consists 

 of 1 — 2 layers. When the shoots have reached a certain 

 age, the central cylinder will be found lying free within a 

 tubular sheath, formed by the lignified and thickened cor- 

 tical parenchyma, together with the persistant epidermis filled 

 with a brown secretion. 



The cells of the cortical parenchyma are elongated axially, 



