cells below the assimilafcory tissue in H. panic/datum (fig. 216) and S. pauciflorum ; it may form a water storing tissue. E. aspera possesses some thick-walled ovoid cells in the assimilatory tissue which may ba of the nature of secretory cells. Cork is well developed and is subepidermal in E. aspera. The endodermis is not differentiated except in H. panic id at um in which it is characterised by granular contents.
The pericycle forms a composite ring of stone-cells in S. pauci- florum ; it is composed of closely placed groups of stone-cells in E. aspera, H. rariflorum, H. panicxdatum and H. undUlatum. It consists of isolated stone-cells in A. hispidissima and of groups of bast fibres in H. supinum. A sclerenchymatous pericycle is not developed in T. indicum, which is quite herbaceous. There are large groups of bast fibres in the soft bast of E. aspera.
The wood forms a composite ring in all members. The perfora- tions of the vessels are simple. It should be observed that in herbaceous members vessels are large and numerous in correspondence with more vigorous transpiration. The development of interfascicular wood prosenohyma is in inverse proportion to the size and abundance of the vessels. The abundance of medullary rays usually corresponds with that of vessels. Some of the vessels towards the pith are found to hold tanniniferous contents. The pith consists of small cells with lignified walls in E. aspera, H. rariflorum and A. hispidissima ; in other members it is formed of very thin- walled cells. The pith cells of II. panicidatum hold granular contents. The pith is strengthened by sieve-sclereids in H. rariflorum (fig. 211 SVJ.
CONVOLVULACEAE.
Cressa cretica L.— Figs. 224, 225. Guard-cells in the same plane. Front cavity in depression produced by outer thickened epidermal walls. Mesophyll isobilateral. Internal secretory organs and oxalate of lime absent. Veins provided with green bundle-sheaths. Clothing hairs two-armed. Glandular hairs horizontal. Pericycle formed of closely placed groups of stone-cells. Assimilatory tissue in the axis formed of palisade cells. Wood composite. Pith of thin-walled cells.
Breweria latifolia Bth. — Figs. 226, 227. Guard-cells on the same plane. Front cavity placed in depression formed by outer thickened epidermal walls. Mesophyll isobilateral. Internal glands in the form of colourless secretory cells surrounded by specialised subsidiary cells in the mesophyll. Clustered crystals near veins, in cortex and pith. Solitary crystals in outer soft bast. Veins provided
