LEAF PRCTECTION. 



289 



In all the three de- 

 vices common to the 

 Heath, the Oleander 

 and the Oldenburgia 

 — namely, the cuticle 

 of wax, the large 

 water-containing- epi- 

 dermis, and the woolly 

 shelter for the stoma- 

 ta — the Oldenburgia 

 is easily first. The 

 wax makes the dry 

 leaf as stiff as a 

 board. While the 

 Oleander has 3 rows 

 of epidermal cells, 

 Explanation.* the Oldeyihurgia has 



A. Cuticle. E. Whip hairs. everywhere 4, and in 



BB. Epiderm. F. Palisade cells. some places as many 



CC. Hypoderni. G. Stellate cells. as 5 or 6. Thus the 



D. Sclerenchymatic tissue. H. Stoma. structure of the leaf is 



a net-work of sclerenchymatic walls dividing- the whole into poly- 

 g-onal compartments : each compartment is occupied bv a dome of 

 g-reen tissue whose head rises above the level of the walls : the 

 whole is then covered by water-cells (4 above the domes, and 6 

 above the walls) ; finally, the upper side is roofed with its strong- 

 cuticle of wax, and the lower side is abundantly pro- 

 vided with matted hairs of the type which the Germans call 

 whip-hairs — a pedestal with one cell for the stick, and a long- cell 

 for the lash. I suppose that during- the rainy season the woolly 

 covering absorbs so much water that the plant has to have an inter- 

 nal atmosphere to be able to breathe at all^ while in dry weather 

 the felt-like covering is effective enough to prevent excessive tran- 

 spiration. 



If I may be pardoned so rudimentary a remark, I should like 

 to tell beginners that the leaf is quite easy to cut even in the 

 dry state, provided of course one cuts from the lower side towards 

 the upper ; even if the section is not very thin, both stellate tissue 

 and stomata are readily demonstrated. 



* This figure is reproduced from a drawing made at the microscope by 

 Miss Margaret Michell of the South African College. 



NEW DOUBLE STARS.— In the Notes on Some Points 

 Connected with the Progress of Astronomy during the year, 

 appended to the 91st Annual Report of the Council of the Royal 

 Astronomical Society, it is stated that Mr. Innes, at Johannesburg, 

 has made careful estimates with the nine-inch Gru^bb refractor of 

 the angles and distances of 268 new double stars, of which 115 

 have a separation of less than one second. This brings Mr. Innes's 

 total discoveries up to 700. 



