Cooke. — Observations on SaJicornia australis. 353 



5. The water tissue of the leaf-base (cortex) is in all parts similar to 

 the mesophyll of the leaf, when this does not consist of palisade-cells. 



6. Below what I regard as the leaf-base the stem loses its palisade 

 tissue (see fig. 3, c). This is a very short portion of each internode, just 

 the part covered by the leaves of the next node below. 



7. A longitudinal section through the growing-point shows the leaf- 

 base of the usual kind, with a very extensive growing-point (see fig. 2). 



Cross-section of the internode before leaf-base disappears shows : — 



(1.) Epidermis, a single layer of cells, the outer walls of which have 

 developed a cuticle. 



(2.) Palisade parenchyma and scattered tracheides. 



(3.) Aqueous tissue, the internal limit of which is the endodermis. 



(4.) Portions of fibro-vascular bundles scattered about in the aqueous 

 tissue. These I regard as the vascular bundles of the leaf-bases. 



(5.) Central cylinder or stele with a well-marked pericycle. This is 

 the only portion in this section which can be called " stem." In this are 

 embedded the collateral fibro-vascular bundles, which in this section are 

 seven in number. 



Cross-section of stem below the leaf -base shows : — 



(1.) A thin -walled epidermis of cells much smaller than those of the 

 leaf. 



(2.) Hypodermis, two cells deep. 



(3.) Cortex of thin- walled parenchymatous cells resembling those of 

 water tissue, only much smaller. Chloroplasts are few in number in com- 

 parison with those of the chlorenchyma in the leaf and leaf -base. 



(4.) Central cylinder. 



There is no cuticle, no stomata, no palisade tissue, no scattered 

 tracheides, and no fibro-vascular bundles except in central cylinder. 



Epidermis of Leaf and Leaf -base. 



The epidermis consists of a single layer of thin-walled cells whose outer 

 walls present cuticular thickenings. The cells of the dorsal differ con- 

 siderably from those of the ventral side of the leaf, the radial walls being 

 short and the tangential long. The outer wall is quite flat, and there are 

 no stomata. On the ventral side a longitudinal section shows the epidermal 

 cells have the vertical diameter about the width of the radial, and the outer 

 walls are raised into small papillae. Surface view shows that the cells 

 are — (a) hexagonal, with sharp corners ; (b) elongated transversely. This 

 transverse extension, according to De Bary (1, d), occurs only in the leaves 

 of several plants or in the stems when palisade tissue is developed in the 

 cortex. It occurs also in the leaves and leaf -bases of Salicornia australis. 

 The nucleus of epidermal cell is large, and when treated with alcohol turns 

 yellow and becomes very obvious. 



As usual in the case of the epidermal cells, there are no chloroplasts 

 except in the guard-cells of the stomata. If, however, the plant is grown 

 under a bell jar, and is watered often, chloroplasts, few in number, may 

 be found in the epidermal cells. Under these conditions the epidermal 

 cells are not elongated transversely, and are wavy in outline. 



The cells of the epidermis of the hypocotyl are very much longer than 

 they are wide, but the elongation this time is longitudinal. Cross-section 

 of hypocotyl shows a number of the epidermal cells dividing periclinally 

 (see fig. 4, e). 

 12— Trans. 



