Finlayson. — Stem-structure of Leafless Plants. 369 



In G. nana the stem is much thinner. There are not so 

 many vascular bundles as in the stem of C. monroi, nor are 

 they opposite each other. The stereom strands reach to the 

 vascular bundle, surrounded on outside by the thin-walled 

 polygonal layer of cells seen also in G. monroi and C. flagelli- 

 formis. The cuticle is not quite so thick as in G. monroi ; the 

 stomata occur in a similar place (above chlorenchyma in the 

 epidermis). The chlorenchyma is palisade, but there are 

 occasional air-cavities (fig. 10b). A few isolated groups of 

 thick-walled cells, with a surrounding ring of thin-walled cells, 

 occur in the chlorenchyma tissue, but these are of minor im- 

 portance owing to their small size. On the inside of the 

 xylem occurs a group of stereom cells ; there may be only 

 a few (as in vascular bundle on right hand of fig. 106), or 

 more (as in vascular bundle on left-hand side of the same 

 figure). The pith-cells are large and polygonal. Since the 

 tissues composing the stems of the three species are similar, 

 a longitudinal section of the stem of G. nana only is given 

 (fig. 106). The stereom cells are seen to be somewhat elon- 

 gated with oblique transverse walls, all the walls being much 

 thickened. (The thin-walled layer of cells is not represented.) 

 The phloem elements include sieve-tubes and phloem paren- 

 chyma (fig. 106, s. t., p. par.), with cambium (cm.) on inside. 

 Xylem elements include spiral vessels (sp. v.), pitted vessels 

 (p. v.), with elongated woody cells between. Inside of the 

 xylem is the stereom tissue, followed by the pith, and on the 

 other side chlorenchyma with epidermis. The opening of the 

 stoma is seen best in longitudinal section. The stomata of all 

 three species are fairly numerous, not very large, with no 

 peculiar structure, and only verv little insunk (figs. 106 and 

 76). 



At the apex of the shoot of C. monroi a violet-coloured 

 fluid (anthocyanin) is present in the inner epidermal cells ; 

 lower down in the stem it is absent ; it is also absent in 

 C. nana. 



The stems of all three species are glabrous. 



In the five species which have been considered, evidently 

 the chief danger to be guarded against is excessive transpira- 

 tion. The total absence of hairs (except in the minute leaf of 

 G. flagelliformis) so commonly occurring in alpine plants 

 shows that it is not a question of loss of heat, but rather of 

 avoidance of excessive heat. This is effected in the case of 

 the Garmichaelias by the vertical position of the shoot-axis, 

 and probably in C. monroi by the development of antho- 

 cyanin in the shoot-apices (the lower parts being protected 

 by the cushion-like form of the plant). Transpiration is 

 checked chiefly by the thick cuticle found in all of them, and 

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