198 Fr. J. Mathiesen. 



depicted (fig. 16, A) is thus only 0.5 mm thick; the paren- 

 chymatous ground tissue, surrounding the numerous ves- 

 sels, is lignified at the periphery of the hadromal part. In 

 the leptome the sieve tubes seem to be few. but their pre- 

 cise determination is made difficult by the rapid thickening 

 of their lateral walls, which in a transverse section makes 

 them resemble the somewhat collenchyma-like parenchyma 

 cells surrounding them. In the periphery of the root, the 

 parenchyma cells appear to be tangentially extended and 

 are frequently divided by thinner radial walls. 



The peduncle. A lacunar tissue of axially extended 

 cells, containing chlorophyll granules, is surrounded by a 

 thick, strongly cuticularised epidermis, provided with stom- 

 ates (fig. 16, B) ; the peduncle is therefore, in this case, an 

 organ with assimilative functions. Inside this tissue is seen 

 a stereome including up to 10 layers of very elongated and 

 thick-walled parenchymatous cells, with finely pitted lateral 

 walls. The first-formed vessels (see fig. 16, B, below) are placed 

 nearly in a radial line, and have only a few ill-defined 

 annular thickenings, so that in the fully developed peduncle, 

 they are found quite flattened by the turgid pressure of the 

 surrounding tissue. The ground-tissue has very thin walls, 

 and often perishes during the ripening of the fruit, when the 

 peduncle becomes hollow. 



The pedicels, about 0.5 mm thick, are very similar in 

 structure to the peduncle. 



The leaf. The epidermis of the upper surface (fig. 

 17, A) has straight, often pitted, lateral walls, those of the 

 lower surface being rather strongly undulated (fig. 17, B). 

 The outer walls show cuticular striations, especially distinct 

 around the hairs. Of these two kinds are present: I. glandu- 

 lar hairs with a one-celled stalk (less frequently two-celled) 

 and with a unicellular head; these originate from a cell 

 which is smaller than the surrounding epidermal cells. 



