Scrophulariaceae. 437 



showed the following structure: Of the exceedingly thin- 

 walled epidermis only scattered fragments were left, the cells 

 were dead and had collapsed. The outermost layer of the 

 cortex had cuticularised outer and lateral walls (it must 

 certainly be this layer which Th. Holm in his Fig. 7, Tab. III, 

 designates epidermis); the layer just within the outermost 

 layer adjoins the latter without or with small intercellular 

 spaces between them; the endodermis has distinct Casparian 

 dots. The intervening part of the cortex consists of a very 

 lacunose tissue, which corresponds exactly with that in the 

 rhizome (shown in Fig. 27, C). Such slender adventitious 

 roots complete their development during one season of growth; 

 their structure is 2-rayed, and by the secondary growth 

 there is formed a bundle of xylem-tissue, about 0.5 mm thick 

 consisting of vessels with intervening non-lignified tissue. 

 Of the individual figured in Fig. 26, 1 a transverse 

 section of the axis was taken from the part between / 

 and //, and also one between // and ///; the former 

 part must be assumed to be 3 years old, and the latter 

 2 years. In the part between / and //, there was found 

 in the stele a circle of vascular bundles, separated by 

 broad, non-lignified, parenchyma-rays (cf. Fig. 27, A, which 

 shows the xylem part of a vascular bundle). In the second 

 year of growth an increase of the vascular elements has 

 evidently taken place, the lowermost (i. e. in the stem inner- 

 most) group of wide vessels probably indicates the limit of 

 the first year's growth; what is found outside that belongs 

 then to a later (probably the second) year. Wood-fibres are 

 quite absent: -e the pith does not die away. Fig. 27, B is 

 drawn from a . on taken from the part between // and ///, 

 at about the middle of it. Here the axis is hollow, because 

 the central part of the pith, as in the peduncle, has died 

 away; the walls of the outermost layers of the pith have 



