Cooke. — Observations on Salicornia australis. 



351 



brunches are very long and thick. Sometimes when the stems are pro- 

 cumbent they are as much as 3 ft. long, and give off adventitious roots 

 at the nodes. Short procumbent branches often become very thick and 

 woody, being sometimes over h in. in diameter. The young branches are 

 cylindrical, green, and succulent, owing to the succulent leaves and leaf- 

 bases which surround them. 



The branching is opposite. In some plants the branches appear to be 

 given off from the main axis, just below the insertion of a branch. These 

 are, in the cases I examined, branches given off 

 from the lowest node of that branch, the node 

 being almost indistinguishable. Sometimes two 

 branches arise together, and are surrounded by 

 leaves (with only slightly developed bases), in 

 the form of a spiral (see fig. 9, c). 



Intermediary 'S^p^ 

 growing-point §&& 



I 



Leaf base ■ 



(2.) Structure. 

 Leaves. 



Thomson, Cheeseman, Laing and Blackwell, 

 and Miss Cross, all following Sir Joseph Hooker, 

 describe Salicornia australis as " leafless," but I 

 find that as long as green tissue remains on the 

 plant leaves persist, and are short and connate 

 — the free portions like decussate scales. At the 

 apex they are only a few cells in thickness, 

 but lower down abundant water tissue is present. 

 The veins are not visible till a section is made. 

 It is the greatly developed leaf-base which forms 

 the " cortex " referred to by writers on Salicornia. 



A longitudinal section of the growing-point 

 shows an apical cone surrounded by leaves. Those 

 near the apex have the base only slightly enlarged. 

 Apical growth of the leaves soon ceases, and inter- 

 calary growth takes place at the base, as in the 

 majority of leaves. This is recognizable by the 

 fact that all the mitotic nuclei are there. The 

 cells containing these nuclei are small and iso- 

 diametrical in shape (fig. 3, b). In leaves further 

 down the stem the mitotic nuclei are still observ- 

 able at the base. Thus this intercalary growing- 

 point proceeds downwards, and gives rise to all 

 the chlorenchyma, as well as all the water tissue 

 of the leaf-base. 



Running down the middle of the dorsal surface 

 of the leaf is a white line, due to the absence of 

 chlorophyll in the underlying tissue. The lower 

 termination of the line marks off the free portion of the leaf from the 

 beginning of the leaf-base. As each whorl of leaves overlaps the bases 

 of the whorl above, the stem is never visible till the leaves have 

 fallen. 



The dorsal surface of the leaf is concave, the ventral convex. The leaf- 

 margins are colourless, since, being only two cells in width, there is no 

 palisade tissue developed between the dorsal and ventral epidermis. 



Fibro-vascular 

 bundle - - 



Fig. 2. — Longitudinal sec- 

 tion of bud, X 1 6. 



