Scrophulariaceae. 451 



xylem-groups of the Ist year, viz., opposite the parenchyma- 

 rays which separate the original vascular bundles. The cork 

 in the primary cortex is constantly few-layered only. 



Lastly, a portion of a rhizome of a 3-year-old shoot with 

 a terminal peduncle, was investigated. The basal portion 

 was found to be unaltered, as described above in the case 

 of the 2-year-old shoot; in the part developed during the 

 2nd year of growth (ill astrated diagrammatically in Fig. 

 32, B), fundamentally, the same development has taken place 

 as that which, in the second year, took place in the basal 

 portion, the only differences being that here the vascular 

 groups are larger and more numerous, and the stereom-caps 

 much thicker, and also that the two zones of growi.h are 

 separated by a ring of non-lignified tissue (parenchyma) as 

 much as 15 cell-layers thick, in which a layer of cork, con- 

 sisting of 3 — 5 layers of cells, is developed ; this layer of cork 

 surrounds, in a tube-like manner, the xylem developed 

 during the first year of growiih. In the figure the cambium 

 is consequently situated immediately outside the outermost 

 circle of xylem-groups; the endodermis is in part distinct, 

 and in the figure, is indicated by a fine line; the two thickly- 

 drawn circles indicate the outer and inner cork-layer; \\ithin 

 the pith there is another one like it, also indicated by a 

 thickly-drawn line; in the outer circle of xylem-groups, the 

 inner, dotted part indicates that this part consists especially 

 of Vessels, the outer radiately-shaded part, that there wood- 

 fibres predominate, in the inner circle where the situation 

 of the vascular- and stereom-elements is less sharply distin- 

 gaishable, the whole of the xylem is shaded. 



Where the rhizome bears the rosette of the 3rd year, 

 it shows a transition to the structure of the peduncle, and 

 gradually merges evenly into the latter — the wood-fibres 

 form an almost continuous ring, and cork-development ceases. 



