296 Transactions. 



Below this tissue there are large groups of pericycle fibres ; these have 

 a small diameter, and their walls are thickened. 



The phloem forms a wide* band, with the sieve-tubes of small diameter ; 

 there is a fairly large amount of phloem parenchyma. The cambium is 

 very easily seen. 



The xylem contains vessels of fairly large diameter and wood-fibres 

 which have very thick walls. There are no medullary rays. 



The pith is solid ; it consists of large roimdish cells with thin walls. 



34. Senecio bellidioides Hook. f. 



Habit. — This is a small rosette plant. The leaves are all radical and 

 spreading ; the blades f-2J in. long, broadly oblong, obtuse, rounded or 

 slightly cordate at the base, membranous, with entire margins ; the upper 

 surface is more or less covered Avith stiff glandular hairs, and the lower 

 is sparingly covered with tomeutum. The petioles are about | in. long, 

 and are covered with hairs. The scapes are 1-12 in. high, branched, and 

 pubescent. 



Anatomy. 



Leaf (figs. 22-26). — Fig. 22 gives a diagrammatic view of the transverse 

 section of the leaf. From this it will be seen that- the number of vascular 

 bundles is small ; the relative frequency of the different types is also seen 

 in this diagram. Fig. 24 shows the structure of the midrib, and fig. 23 of 

 the blade of the leaf. 



The upper epidermis consists of rather small cells, the outer walls of 

 which are slightly thickened. There is a thin cuticle present. Stomata 

 are found on both surfaces ; the guard-cells are level with the surface, 

 and have thickened walls and small guard-cell ridges. Some of the upper 

 epidermal cells are produced into hairs of two kinds — 



(1.) Capitate glandular hairs : These are very long, and are m\ilti- 



cellular, and have a roimded head. 

 (2.) There are also other multicellular hairs formed of about 9 cells. 

 At the base there are about 7 small rectangular cells which are 

 closely packed together and have their outer walls slightly 

 cuticularized. Above these cells there is a large, wide, and 

 shallow cell which has a thick but uncutinized wall. Beyond 

 this cell there is an elongated one, also with a thickened, 

 imcutinized wall. 

 The lower epidermis also consists of cells which are more or less oval 

 in transverse section. They have thin walls, except for the external ones, 

 which are slightly thickened. There is a thin cuticle. Stomata are 

 present on this surface also. The epidermal cells contain a few chloro- 

 plasts. Some of the epidermal cells give rise to hairs of two kinds — 

 (1.) There are a few glandular hairs as on the upper surface. 

 (2.) Most of the hairs are like those on the upper surface, except that 

 there are usually only 4 of the small cells and there are 2 long 

 cells instead of 1. 

 The chlorenchvma is only slightly differentiated. The palisade tissue 

 consists of 2 rows of cells, which have thin walls and contain numerous 

 chloroplasts. These cells are wide and do not have the typical palisade 

 form ; they are fairly loosely arranged, so that there are large air-spaces 

 between the cells. 



