Scrophulariaceae. 375 



easily discernable, since they are separated by a zone in 

 which the vessels and wood-fibres are intermixed with non- 

 lignified, axially elongated parenchymatous elements. 



The Stem. In the lower persistent parts of the stems, 

 a cork-cambium commences activity during their second 

 year; it appears in the outermost layer of the cortex and 

 forms a few-layered cork (Fig. 3). The cells of the primary 

 cortex are rather thick-walled and show division by radial 

 walls; they contain chlorophyll-grains. The endodermis has 

 very distinct Casparian dots (as in the root). In the 

 pericycle small groups of hard-bast cells are found. The 

 figure shows a portion of the transverse section of a stem 

 with apparently two growth-rings; between the two rings 

 consisting of vessels and wood-fibres there is a zone inter- 

 mixed with thin-walled and non-lignified cells; however, in 

 reality the stem is 3 years old; during the first year only 

 the innermost zone of the xylem with the small scattered 

 vessels being developed. According to whether the shoots 

 during the first year succeed in becoming more or less 

 vigorous, so also does the thickness of the xylem of the 

 first year vary; shoots may sometimes be found in which 

 a continuous wood-ring has been developed as in the follow- 

 ing years. 



In the upper part of the shoot which dies away, no 

 cork-formation takes place, the cortical cells are less thick- 

 walled than in the lower part and richer in chlorophyll and 

 Casparian dots are less distinctly developed. Hard bast is 

 wanting or is scantily present in the pericycle, and the wood- 

 ring is quite narrow. From all the axial organs medullary 

 rays are quite absent. 



The Anatomy of the Leaf has been investigated by 

 Koch and Huchedé; my investigations entirely bear out 

 the conclusions arrived at by them. The epidermal cells of 



