Betts. — Autecology of Plants of Ptridofife Belt, Nelson. 149 



Inside this zone of tissue there is a band of colourless cortical tissue : 

 this is composed of large roundish or polygonal cells, forming a compact 

 tissue with only very small intercellular air-spaces. These cells are colour- 

 less, and form a water-storage tissue. 



Above the phloem of the bundles there is a small group of pericycle 

 fibres with thick walls and small cavities. Above the fibres there is a duct 

 of large diameter, lined by about 8 epithelial cells. The phloem is a narrow 

 band of small elements ; the cambium, 2 rows of cells, can be clearly 

 seen. The xylem consists of vessels of fairly large diameter and of xylem 

 parenchyma. 



All the ground-tissue internal to the water-tissue is lignified. The 

 3 or 4 rows of cells adjacent to the water-tissue are small, thick- walled, 

 and compactly arranged. Passing inwards from this tlie cells become 

 larger and their cell-walls thinner, but they are still lignified. There are 

 large intercellular air-spaces where 3 or more cells meet. The stem is 

 hollow. 



19. Anisotome aromaticum Hook, f. var. 



Growth-form. — A small aromatic herb, matted and depressed, 1-2^ in. 

 high. The root is stout, long, and tapering. The stem is simple. The 

 leaves are all radictil, numerous, 1-6 in. long ; the blade is linear and 

 pinnate ; the leaflets are in 6-12 pair;-;, ^-| in. long, more or less incised ; 

 the lobes end in a bristle-like point. The petiole is short, stout, and broadly 

 sheathing at the base. 



Anatomy. 



Leaf (figs. 14, 15). — Fig. 14 shows the form of the leaf, and fig. 15 gives 

 a diagrammatic view of the transverse section. 



The upper epidermis consists of fairly large squarish cells with thick 

 walls. A thick cuticle is present, forming a minute papilla above each 

 cell. There are no stomates on the upper surface. The lower e})idermis 

 consists of smaller cells than the upper ; the walls are thickened, and there 

 is a thick smooth cuticle. Stomates are confined to the lower surface, 

 where they are slightly raised above the epidermis. The stoma is pro- 

 tected by guard-cell ridges. Beneath the upper epidermis there is a hypo- 

 derma, fortaed of thick-walled cells like those of the upper epidermis ; these 

 cells contain a few small chloroplasts. 



The palisade tissue is formed of 2 rows of cells, which are small, thin- 

 wallc^d, closely packed together, and contain numerous chloroplasts. The 

 spongy tissue consists of irregular cells, with the walls slightly thickened ; 

 they are loosely arranged, and contain numerous chloroplasts. The meso- 

 phyll cells just above the lower epidermis are much smaller, are rounded, 

 and are closely packed together. 



The vascular bundles are surrounded by a sheath of thin-walled paien- 

 chymatous cells, which contain a very few chloroplasts. The amount of 

 lignified tissue in the xylem is small. Above the xylem and below the 

 phloem there are ducts lined by a single layer of small epithelial cells. The 

 duct below the phloem is much larger in diameter than that adjacent to 

 the xylem. 



Peduncle (fig. 16.) — The epidermis consists of very small rounded or 

 squarish cells, with thickened walls and a fairly thick cuticle. 



The outer 3 or 4 rows of cortical cells are small round cells, with very 

 thick walls and no air-spaces between the cells. The remaining part of 



