BY Jt)HN SHIRLEY, D.SC, AND C. A. LAMBERT. 47 



•cell thick. In all positions it hc\s a derinal layer, two cells 

 in thickness, giving the leactions in the cell-Avall for true 

 cellulose. These cell walls are gi-eatly streugthsned and absorb 

 colour readily. In re-entering angles thi dermal layer, 

 or coUenchyma, may be 4-5 cells thick. In places the 

 strengthening layers have almost obliterated the cell cavity. 

 In other respects the structure is that normal to tlie order. 

 Plate VII., Figs. 1. 2. 



VIT — Rhipsalis suUroinoides. D.C. 



The thong-like stems of this plant, an epi|)hyte from 

 the American forests, are in structure more like the stem 

 oi an ordinary dicotyledon, than any other yet examined. 

 The stele contains numerous wood v'essels, mostly s]>iral, 

 but has the central aqueous tissue of the Cact?e instead of 

 pith. The cortical regions, as shewn in longitudinal 

 sections, are filled with the usual air-cavities, joined by 

 tubes or passages to the stomata. All the cells — palisade 

 <?ells and medullary tissue — are very minute. Crystals of 

 oxalate of lime, in rhouiboidal or irregular masses, are 

 found mainly in the stele, and especially near the woodj- 

 tissue 



