Betts. — Autecology of Plants of Peridotite Belt, Nelson. 211 



The medullary rays are uniseriate, frequent, and have thickened, 

 lignified walls, and contain tannin. 



The pith is solid, and is composed of large polygonal cells with thick, 

 lignified, and pitted walls. The cells contain tannin. 



26. Gentiana corymbifera T. Kirk. 



Habit. — The plant is a perennial herb. The root is stout, long, and 

 tapering. The stems are simple and rarely branched from the base, 

 stout, erect, terete, 6-20 in. high. The leaves are both radical and 

 cauline. The radical leaves are numerous, rosulate, \-2\ in. long, |— ^ in. 

 broad, narrowed into a short petiole. The blade is coriaceous, and rather 

 thick and fleshy. The cauline leaves are few in number, f-lj in. long, 

 linear-lanceolate, and sessile. 



Anatomy. 



Leaf. — The upper epidermis is composed of large cells which in trans- 

 verse section are oval. They have all their walls, and especially the 

 external ones, thickened. These cells contain drops of oil. There is a 

 thin, rough cuticle. 



The lower epidermis is the same as the upper, except that the cells are 

 somewhat smaller. There is a thin cuticle on this surface also. Stomata 

 are found on both surfaces, but are much more numerous on the lower. 

 The guard-cells are small, and have very thick walls. The stoma is 

 protected by guard-cell ridges which are rathqr large. 



The chlorenchyma is differentiated into palisade and spongy tissue. 

 The palisade tissue consists of 5 rows of large cells with slightly thickened 

 walls. These cells contain ver)'' numerous small chloroplasts, and there 

 are small air-spaces between the cells. 



The spongy tissue is composed of large, irregular cells, the walls of which 

 are only slightly thickened. There are quite large intercellular air-spaces 

 in this tissue. These cells contain a thin layer of protoplasm in which 

 are embedded small chloroplasts, which are not nearly as numerous as in 

 the palisade tissue ; these cells serve as water-storage cells. 



The vascular bundles are small and numerous ; associated with both 

 the phloem and the xylem there is parenchyma. The bundle is surrounded 

 by a sheath of thin-walled parenchymatous cells which contain a few 

 chloroplasts. Below the main bundle there is a small amount of collen- 

 ohyma. 



Stem. — The epidermis is composed of cells which are large and rounded' 

 in transverse section. They have all their walls very much thickened, 

 and there is also a moderately thick, rough cuticle. Some of the epidermal 

 cells contain drops of oil. 



Below the epidermis there is a well-marked hypoderma. This consists 

 of cells which are the same as the epidermal cells, and they also have their 

 external walls cuticularized. The hypoderma is in places separated from 

 the epidermis by a large air-space. 



The cortex is a wide band ; it is composed of large, more or less oval 

 cells which have their walls somewhat thickened. There are very small 

 intercellular air-spaces in this tissue. In the outer part of the cortex the 

 cells contain a few small chloroplasts. All the cortical cells form an 

 aqueous tissue. The endodermis is well marked ; it is a layer of large 

 cells with thin suberized walls. 



