324 HALF-AN-HOFR AT 



Glandular Hairs of Sweet Briar (PI. X,, lower portion) are 

 specially beautiful in the fresh state. Their interior is seen to be 

 filled with soft, secreting, cellular tissue, and the tip to have a 

 little projection of the fragrant essential oil, or " attar of roses " ; 

 this may be separated in a semi-crystalline condition by a little 

 manipulation on the stage of the microscope. 



Scalariform Ducts (PL XL, Figs, i — 6). — Different portions of 

 these ducts vary greatly in the extent to which the regular ladder- 

 like {scala, a ladder) structure is developed, as may readily be seen 

 by examining the examples before us with high powers. Some- 

 times the latter deposits include two, or even three, of the earlier 

 pores. vScalariform tissue is by no means confined exclusively 

 to ferns. Good examples occur in the stems of Bryony, Vege- 

 table Marrow, Cucumber, and the Eryngo or Sea Holly. 



Sections of Fir (PL XII., Figs, i — 3). — To show the structure 

 of wood in the Scotch fir, sections should be mounted in glycerine 

 or chloride of calcium. 



Disc of Ophiocoma (PL XL, lower portion). — I have not Forbes 

 British star-fishes at hand, but believe this to be from O. bellis, 

 the Daisy star-fish ; the colour is natural and well preserved. I 

 expect the white specimen alluded to by a member to be 

 bleached. Different species of this genus vary much in size at 

 maturity and the larger forms according to age. They cover from 

 a mere point to a circle of seven inches in diameter or upwards, 

 with a disc three-quarters of an inch across. The teeth of Echini 

 furnish examples of, perhaps, the most wonderfully elaborate 

 architecture to be met with in the whole animal kingdom. I have 

 not specially examined the teeth of Ophiocoma, but am informed 

 that they are simple, and make no approach to the complexity of 

 those named. 



Tongue of Trochus (PL XII., central portion). — I lately picked 

 out several from a pint of " winkles " brought to the door for sale. 

 Some species grow to a noble size ; they are commonly known by 

 the name of Top-shells. 



In systematic description the teeth are said to be arranged in 

 different series and described accordingly ; thus, we have here 



