168 THE AMERICAN MONTHLY [June, 



the prism case put in its place, the ocular being inserted in the 

 short tube provided for its reception. The ocular should point 

 downward. The lamp or other source of light should then be 

 disposed in such a way that it properly illuminates the object to 

 be examined, it being expressly understood that no light shall 

 escape toward the observer except that which first reaches the 

 object. A Beck lamp is conveniently adapted to this purpose. 

 If a piece of drawing-paper is placed beneath the ocular, and the 

 room darkened, a brilhant image will be projected on the paper, 

 and its reproduction can be easily accomplished with a maximum 

 of rapidity and a minimum of discomfort. In guiding the pencil 

 the draughtsman uses both eyes, and his spectacles if needed, 

 and sits in whatever position he finds most comfortable. With a 

 proper lamp, and careful utilization of its light, this device gives 

 excellent results, with amplification up to four or five himdred 

 diameters. If a sensitive photographic plate be substituted for the 

 drawing-paper, an exposure of a few seconds will impress an 

 image that may be developed in the usual way. — New York 

 Medical Jo u rnal. 



Spiral Vessels of Castor-Oil Plant. 



From Note-book L of the American Postal Microscopical Club. 

 By R. H. ward, M. D., 



TROY, N. Y. 



For the study of this specimen use only powers of 2 in. to 

 4-ioths in., or for the special piu'pose mentioned hereafter a low- 

 angled I -5th or I -6th ; as the contour of the spirals shows best with 

 objectives of greatest available depth of field, and higher powers 

 are unnecessary. Most satisfactory stereoscopic views can be got 

 with the VVenham binocular and a 1-2 to 4-ioths objective, with 

 special illuminating arrangement for working the binocular at its 

 best with medium or higher powers — by. means of a horizontal- 

 slit diaphragm combined with a substage condenser, as introduced 

 by the writer at the Am. Ass'n for the Adv. of Sci. in 1S70 (see 

 Am. Nat.., 1870, pp. 635-8) and used with satisfaction ever 

 since that time. * * * 



This specimen, by the remarkable compactness of its spirals, 

 suggests its probable origin near the outside of an already formed 

 portion of the plant, as those which are formed in the bundles 

 around the pith of a rapidlv growing shoot commonly have the 

 convolutions spread into an open spiral by the elongation mean- 

 while occin-ring in the tissues. This plant {Ricinus covimunis) 

 has long ago been noticed as furnishing " very striking examples " 

 (Sachs) of these spirals in the stalk {rach/s) of its flowers. 



The slide presents a field for a little practice in microscopical 

 mechanics of the easier sort. The cylinders of coiled fibres 

 which line the ducts are formed, in various plants, of single fibres 



