1881.] 



MICROSCOPICAL JOURNAL. 



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125 



to be a structureless, hyaline mem- 

 brane, with stomata openings un- 

 marked (Fig. 9, a, b). Remnants of 

 the cell-walls are left attached when 

 it is stripped off, leaving the outlines 

 of the cells visible as clear hyaline 

 lines (Fig. 9, c) ; often a layer of 

 parenchymal cells remains attached 

 (Fig. 9, d). The structure of the 

 stomata remains in the tiers of cells 

 joining the cuticle (Fig. 9, e). The 

 hairs are shown in Fig. 7. 



The cuticle of the upper surface 

 appears smaller celled, by reason of 

 the parenchymal cells being attached 

 endwise ; and the loose or scattering 

 appearance of the cells arises from 

 the cell contents being shrunken, and 

 the cells being in two tiers. When 

 the upper cuticle is cleanly stripped 

 off, it is found to be hyaline, and dis- 

 closes at its edge, flat, scale-like cells, 

 adhering to its under side (Fig. 3, a), 

 having a hyaline, scale-like substance ' 

 enclosed. On the inside it shows 

 the walls of the parenchymal cells 

 adhering to the layer of scale-like 

 cells (Fig. 4, a). On the large veins 

 the cells of the upper cuticle are 

 long, and arranged like brick work 

 (Fig. 10, b). The cells of parenchy- 

 ma forming the substance of the 

 leaves are of various irregular shapes, 

 but usually about twice as long as 

 their width ; many are triangular or 

 T-shaped, and they are never, so far 

 as I have observed, circular or oval. 

 The most common shapes are shown 

 in Fig. 6. The leaves of the very 

 cheap tea above referred to were 

 found to consist mostly of leaves hav- 

 ing the shape of tea-leaves, but some- 

 what smaller, and of a yellowish 

 tinge. The cells were of very similar 

 shape and arrangement to those of 

 tea, but considerably smaller. The 

 hairs were also of the same shape and 

 size, but they were hollow quite to 

 the tips ; and so numerous, that in 

 some places the leaf seemed entirely 

 covered with them. The stomata 

 were of the same size and shape as 

 those of the tea-leaf ; and on the 

 whole, it seems probable that these 



leaves were actually the leaves of 

 some species of tea. The other im- 

 purities found cannot be described in 

 detail, within the limits of this article. 

 The adulteration is readily detected, 

 however, by a knowledge of the 

 structure of the leaves of genuine 

 tea-leaves. 



The Epidermal Organs of 

 Plants. 



BY CHARLES F. COX, F.R.M.S. 

 (Continued.) 



I will now pass to the physiological 

 portion of my subject. 



It is not to be doubted that such 

 highly developed and specialized 

 organs as plant-hairs have an im- 

 portant physiological office in the 

 vegetable economy. Neither is it to 

 be supposed that so large a part 

 of the mere bulk of the plant is 

 practically useless or only ornament- 

 al. The fact that the hairs of 

 plants constitute a very large propor- 

 tion of their substance, argues that 

 they are not accidental or merely in- 

 cidental growths, but that they must 

 be exceedingly important organs to 

 warrant such an expenditure of ma- 

 terial and energy as is necessary for 

 their production. We all appreciate 

 the extraordinary quantity of mater- 

 ial used to form the seed-hairs which 

 constitute the commercial article, 

 cotton ; and all have observed 

 the also lavish use of material made 

 to produce the seed-hairs of the 

 milk-weed and the thistle. These 

 seed-hairs serve a useful purpose in 

 the distribution of the seeds to a dis- 

 tance, thus disseminating the species 

 to which they belong ; but aside from 

 this I believe that, in common with 

 other plant-hairs, they serve an im- 

 portant physiological purpose before 

 the seeds upon which they grow at- 

 tain maturity. 



It seems to me that light is 

 thrown upon the office of plant- 

 hairs in general, by what we know 

 of the physiological uses of root- 



