66 THE JOURNAL OF INDIAN BOTANY. 



cells below the assimilafcory tissue in H. panic/datum (fig. 216) and 

 S. pauciflorum ; it may form a water storing tissue. E. aspera pos- 

 sesses 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 con- 

 sists 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 her- 

 baceous 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 



