292 Transactions. 



arranged, the inner layer consisting of mucli larger cells than the outer. 

 These cells are roundish or squarish in section, but the rest of the cells of 

 the aqueous tissue are very irregular in outline. They lie close together, 

 so that the intercellular air-spaces are minute. 



Peduncle (fig. 18). — The epidermis consists of somewhat irregular cells 

 which have very thick walls, especially the external ones. From some of 

 the epidermal cells there are produced long multicellular hairs like those 

 on the under-surface of the leaf. A thin cuticle is present ; its surface 

 presents numerous very fine ridges. 



Below the epidermis there is a zone of dead cortex, consisting of very 

 irregular, thick-walled cells with brown contents. The rest of the ground- 

 tissue of the stem consists of lignified tissue. This can be divided into 

 two regions — 



(1.) An outer region where the vascular bundles are found. The' cells 

 in this region are rather small and have thick walls. 



(2.) An inner pith in which the cells have thin but lignified walls. 

 These cells are large and roundish. Small intercellular air- 

 spaces are found in this tissue. The stem is hollow. 



The vasculai bundles are small and quite separate from one another. 

 There is parenchyma in both the phloem and the xylem. The scleren- 

 chymatous cells around the bundles are small. 



31. Olearia virgata Hook. f. 



Hahit. — This plant is an erect, much-branched shrub, 2-5 ft. high. 

 The branches are spreading, tetragonous when young, almost terete in the 

 older parts. The young branches are pubescent. The bark is dark red- 

 brown. The leaves are opposite, obtuse, narrowed into a very short petiole, 

 glabrous above and clothed with white tomentum beneath. 



Anatomy. 



Leaf (fig. 19). — The upper epidermis consists of medium-sized oblong 

 cells ; these have thin lateral and internal walls, but the external walls are 

 thickened, and in addition there is a cuticle, which is, however, only a thin 

 one. There are no stomata on the upjDer surface. 



The lower epidermis is like the upper, but the external walls are not 

 thickened, and many of the epidermal cells are produced into large 

 T-shaped hairs, which are closely appressed to the surface. 



The stomata are confined to the lower epidermis, and they are raised 

 above the epidermal cells. The guard-cells are small and have thickened 

 walls. 



The chlorenchyma is differentiated. The palisade tissue consists of 2 

 rows of closely packed cells, the depth of which is only about one and a 

 half times the breadth. The cells are thin- walled and contain numerous 

 large chloroplasts. 



The spongy tissue consists of 4 or 5 layers of irregular thin-walled cells 

 with large air-spaces between them. These cells contain numerous chloro- 

 plasts, which are slightly smaller than those in the palisade tissue. The 

 cells of the layer just above the lower epidermis are smaller and are more 

 closely arranged. 



The vascular bundle is small, and like that in Celmisia longifolia var. 

 gracilenta except that there is no stereome. The vascular bundle is sur- 

 rounded by a sheath of small, thin-walled, parenchymatous cells which 

 contain a few chloroplasts arranged along their outside walls. 



