Foweraker. — Mat-plants and Cushion-plants of Cass River Bed. 31 



(4.) Morphology. — (a.) Stem. — The stem is wiry, creeping and rooting. 

 The main stems are horizontal and covered more or less with humus. The 

 colour is a light brown, and the exterior is smooth, as the cortex does not 

 fall away from this species so early as in the various species already described. 



The branchlets have a flabellate form, with distinctly distichous leaves 

 In this respect they stand alone among the types considered, and, indeed, 

 among the whole genus. They average about 1 cm. in length and 04 cm. 

 in breadth. At least half the branchlet is clothed with the strongly con- 

 duplicate leaves. The branchlets are by no means compacted together, 

 so that the mat hardly presents a " surface : ' in the ordinary sense. The 

 flabellate form of the branchlets is accentuated by the recurving exhibited 

 by the leaves. 



Transverse sections of a young stem show the same appearance as in 

 the other species of Raoulia ; indeed, the differences between the young 

 stems of all the species are but slight. 



In an old stem secondary growth soon commences, and, as in the other 

 Raoulias, the pith soon becomes lignified. 



A peculiar feature of the stem is the mode of growth of the bands of 

 stereome -fibres in the pericycle. As soon as secondary thickening has well 

 begun certain groups of cells in the pericycle begin to lignify, and this 

 lignification extends langentially until it forms a complete cylinder (fig. 10). 

 The stereome groups commence oppo- 

 site the primary vascular bundles. 

 This stereome-cylinder connects on to 

 the secondary wood at certain points. 

 These points number from four to six, 

 and are opposite the primary medul- 

 lary rays. The cortex suberizes from 

 the exterior inwards and falls away 

 gradually. 



(b.) Leaf. — The leaves are oblong, 

 with parallel edges and bluntly rounded 

 tip, and arranged in two rows on the 

 branchlets. The basal portion sheathes 



a part of the stem and the base of the leaf next above it. Both surfaces are 

 covered with a dense white silky tomentum, especially the inner (upper) 

 surface. The leaves are folded inwards along the midrib, and the dense 

 mass of tomentum on the upper surface entirely fills the groove formed by 

 the folding of the leaf. Owing to the apparent distichous arrangement of 

 the leaves, there is no terminal rosette, as is so characteristic of the other 

 Raoulias. 



The proportionate amount of tomentum in the terminal bud is shown in 



fig- 11- 



The contour of the leaf in transverse section is V-shaped, with the space 

 between the arms densely filled with tomentum. 



The leaf-anatomy is as follows : — Epidermis : Cells on upper surface 

 flatter than below. Cuticle thinnish, same on both surfaces. Stomata 

 on both surfaces ; normal ; sunken on lower surface, raised on upper. 

 Hairs usual Raoulia type. Anthocyan in a few isolated cells in some .leaves ; 

 in others it fills all cells. Chlorenchyma : 'Cylindric cells right round leaf ; 

 very dense at margins ; two cells deep, except at midrib, where layer is 

 single. Nearly every cell contains a large oil-drop. Water-tissue : About 

 three layers of roundish cells ; very few intercellular spaces ; scanty chloro- 

 phyll. Vascular bundles normal. 



Fig. 11. — Diagram of transverse section 

 of rosette of Raoulia Monroi. 



