1881.] 



MICKOSCOPICAL JOURNAL. 



109 



' Before passing to another division 

 of my subject, I must say a few 

 words about stomata, which also are 

 epidermal structures. As a general 

 rule they are found upon the same 

 parts as the hairs and glands, and in 

 the same relative proportions. That 

 is to say, they abound upon leaves 

 and homologous parts, and on young 

 and growing stems and branches ; 

 and they are found in most abun- 

 dance on the under side of leaves. 

 Unlike hairs, however, they never 

 appear upon the mid-rib and veins, 

 but are always found directly over 

 intercellular spaces, of which they are 

 the means of communication with the 

 external air. Of course they are use- 

 less, and therefore exist but as strag- 

 glers, if at all, on parts not exposed 

 to the air. They are therefore not 

 usually found on true roots or sub- 

 merged parts of aquatic plants. Like 

 hairs, their relative number upon the 

 upper and upon the lower side of the 

 leaf depends in great measure upon 

 the natural position of the leaf with 

 reference to the light. 



^To be continued?) 



Sidle's New Mechanical Stage. 



In the April number of this Journal 

 was a notice of our mechanical stage. 

 This having occasioned a host of 

 inquiries, we now publish, for the 

 first time, a short description of it. 



The general plan of our new 

 mechanical stage is similar to that 

 lately introduced by Mr. R. B. Tolles, 

 of Boston. The stage has rectangu- 

 lar motions of one inch, actuated by 

 rack and pinion movements of great 

 smoothness. The milled pinion-heads 

 are on the upper surface of the stage, 

 and, both being on the same axis, are 

 readily accessible in any position of 

 stage without changing the position 

 of the hand. The stage allows of an 

 entire rotation — the pinion-heads be- 

 ing always within its circumference. 

 The entire thickness of the stage, 

 from top to the bottom of the outer 

 ring, approximates .25 inch. Not- 



withstanding this extreme thinness, 

 we have, by the use of hard rolled 

 German silver and brass, succeeded 

 in making it perfectly firm. It might 

 be still further reduced, but we have 

 decided, after mature consideration, 

 that the interchangeable feature, spo- 

 ken of further on, combined with a 

 good, stiff stage, free from spring, 

 affords more practical advantages than 

 would any further reduction in thick- 

 ness. 



The mechanical, together with the 

 plain stage, accompanies our "Acme " 

 No 2 stands. The two stages are in- 

 terchangeable by a simple spring- 

 clip arrangement which permits of 

 the instant exchange, and insures 

 smooth motion in rotation. The ring, 

 or bed-plate, in which these stages 

 rest, is provided with centering screws 

 and is finely graduated. 



This stage, with ring or bed-plate, 

 can readily be adapted to any stand 

 that will admit of a stage five inches 

 in diameter. 



J. W. Sidle & Co. 



Lancaster, Pa. 



The Study of Infusoria.* 



BY DR. S.jO. GLEASON. 



Infusoria are microscopic crea- 

 tures, very minute, of almost end- 

 less variety, found in infusions of 

 animal or vegetable matter. In their 

 adult or complete fotm they are 

 furnished with prehensile or locomo- 

 tive appendages, in the form of cilia, 

 flagella and tentaculas. They are uni- 

 cellular, free or sedentary, live in a 

 mucilaginous matrix, single, or united 

 in colonies. Food is incepted into 

 a distinct oral aperture, through a 

 limited terminal region, or through 

 the entire surface of the body. They 

 increase by longitudinal or transverse 

 fission, and by external or internal 

 gemmation, preceded by a quiescent or 

 encysted state, resulting in a greater 

 or less number of sporular bodies. 



* Abstract of an article read before the 

 Elmira Microscopical Society, February 24th. 



