FICUS ELASTICA (India-Rubber Plant) a tropical forest-tree with leaf afford- 

 ing a good example of high specialization: the lamina 18 in. by 7, with stout petiole, 

 3-4 in.; midrib, pinnate venation, entire margin, and connecting marginal vein, 

 much on plan of Cherry Laurel. Section at right-angles to the small lateral veins 

 more satisfactory: lamina -7 mm. thick, and highly differentiated. In sect, of fresh 

 material note : 



(1) Epidermis, a remarkable aqueous system of 3 rows of cells (originally i), 

 outermost about io/z, next 40 /a, inner ioo/i; total 1 50 p of aqueous tissue as pro- 

 tective screen. Cuticle and cuticularized layers uniformly thick, 7 p. ; at intervals oval 

 cells enlarge to 200 /* long, and show peculiar concretions (Cystoliths) as partly crystal- 

 line deposits of CaCO 3 on a cellulose basis ; sol. in HA, and test Chlor. Zn. lod. for 

 blue cellulose rest and peg : stratified and striated organization suggestive of that of 

 wall-deposits, and of starch-grains. Function unknown, except as * waste '. 



(2) Palisade Mesophyll, of 2 well-marked tiers, leading to a third, in cande- 

 labrum type ; cells 40-50 /A by 12 wide, thin-walled, with abundant discoid chloro- 

 plasts, grading into spongy mesophyll of loose tissue aggregated around V.B. of veins. 



(3) Vascular Bundles, larger ones cut transversely, with x on upper surface ; 

 broad crescentic tract of scl. fibres on lower (</>) side ; small phloem units between ; 

 palisade tissue divergent to make way for them. 



(4) Lower Surface with attempts at a lower palisade (one row); 3-layered 

 epidermis on reduced scale ; occasional cystoliths, and conspicuously fine sunk 

 stomata. 



(5) Stomata, guard-cells sunk midway in aqueous epidermis, 40 \L below level 

 of surface, with thick outer and inner walls, mere slit-lumen, with chlorophyll and 

 starch ; slit hour-glass shaped. Cuticle follows entire contour, and ledges define 

 outer and inner pore-chambers. Large outer vestibule, 30 /x deep and wide. Stomata 

 are cut in all directions in the same section, as many as 4-5 in the field of high power 

 at same time. Well-differentiated in Chlor. Zn. lod. 



(6) Midrib of generalized organization ; parenchyma and V.B. may show abun- 

 dant calc. oxalate rhombs. 



NYMPH A EA, the leaves of the Water-Lily present a quite different type, as 

 associated with flotation on the surface of water. The lamina is soft, 10 in. by 8, 

 with petiole of several feet in length adjusted to the depth of the water, and is over 

 i mm. thick. In sect, note : 



The upper epidermis consists of a single layer of small aqueous cells with thin 

 cuticle. Stomata occur only on the upper surface ; the guard-cells being well supplied 

 with starch-granules, and flush with the outer surface. 



The palisade is very pronounced, 200 /* deep, of short slender, thin-walled cells, 

 in vertical rows, with large discoid chloroplasts, 5 /*. 



The spongy mesophyll is arranged to form rectangular lacunae, bounded with 

 plates of simple cells, in single series, with chloroplasts and nuclei (io/i) in a peri- 

 pheral layer. V.B. rudimentary with spiral tracheides. Remarkable sckrites, as 

 branched sclerenchymatous fibres, pushing irregularly between other cells in all direc- 

 tions (instead of in one line only), are left more or less suspended in the walls of the 

 lacunae on final distension of the lamina : these are lignified, picked out very prettily 

 by the phloroglucin-reaction. The lower surface shows tannin-sacs in the place of 

 more usual stomata. 



Lavandula (Lavender) affords a good example of hair-derivatives of the epider- 

 mis ; as (i) branched hairs, of shrubby growth of dead air-containing units, forming 

 a protective screen over surface, and covering (2) glandular hairs, with 2-4 celled head 

 on short pedicel. The head-cells secrete ethereal oil underneath the impervious cuticle, 

 which may become enormously distended before rupture (60 /*). 



Pelargonium tomentosum, intense odour, softly hairy; (i) simple dead hairs, 

 i mm. long, as velvety pile ; (2) glandular hairs on long pedicels, globular head-cell 60 /* 

 diam. ; secretion distended 80 /*. 



Hedera (Ivy) affords pretty stellate hairs, protective on young shoots ; esp. larger 

 forms with rusty tomentum : limiting case in peltate closely-set scales of Eleagnus, as 

 glistening skin over transpiring surface. 



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