1892.] 



THE MICROSCOPE. 



157 



53. W/io are the workers ofi J^. W. sponges^ and what litera- 

 ture is available ? — Bullard. 



Fresh-water Sponges, by Edward Potts, published by the Acad- 

 emy of Natural Sciences, Philadelphia, Pa., 1SS7, octavo, paper. 

 Rev. C. H. Rowley, Townsend, Mass., prepares sections. The 

 Microscope, vol. VII, has two papers by Henry Mills. 



The Microscope, vol. X, contains a series of papers, very full, 

 by Ed. Potts. 



The Ai7i. Mo. Mic.Jour7zal^ vol. IX, contains two papers also 

 by the above author. 



54. What are " strewn mounts " ? 



This term is applied to diatom mounts which contain all the 

 forms of a certain specimen of earth evenly distributed on one cover. 



NCV/S TRp/A 

 THE Vs/ORKERS 



The Potato. — What may be learned by a microscopical 

 study of the potato is described at length by Professor Osborn 

 in the Journal. Not the least curious is the position of the buds, 

 as shown in figure i . Let any one take a well-formed potato 

 and with a pencil connect the eyes as shown in the figure and 

 then number the eyes in order. It will be found that the 12th 

 is under the 17th, the 7th under the 12th, the 2d under the 7th, 

 etc. ; add 5 to the number of an}^ eye and it gives you the number 

 of the eye directly over it. 



EXPLANATION OF PLATE. 



(All figures were drawn with the Camera Lucida.) 



Fig. I. Surface view of tuber, showing the 

 law of position of the buds, x 7/3 natural size. 



Fig. 2. Vertical section of the stem through 

 a bud, showing the bud with its terminal por- 

 tion at b, and its leaves at a, with the thin 

 layer of bark and the pith in which, parallel 

 with the bark, lies the fibro- vascular layer. 



Fig. 3. Vertical section of stem magnified 

 133 diameters, showing (i) the bark cells at c 

 in rows, the edges of which produce the par- 

 allel lines seen in the surface view (Hig. 4); 

 (2) the living subdermal cells specialized as 

 starch producers. The uppermost are full of 

 protoplasm (at d in the figure); below them 

 are cells containing large vacuoles and in which 

 the starch grains are forming (cf. figs. 7, 8, 9). 

 There are only a few rows of these before the 



cells filled with starch are reached at st in the 

 same figure. 



Fig. 4. Surface view of theiark cells mag- 

 nified 133 diameters. 



Fig. 5. Flat view of cells immediately be- 

 low the bark from the level marked d in fig. 3. 

 After treatment with weak acid these cells, 

 before irrigation ol the acid, appeared to be 

 absolutely empty. 



Figs. 6, 7, 8. Greatly enlarged views of nu- 

 cleus and surrounding protoplasm from cells 

 at level of e in fig. 3, showing the starch 

 granules surrounded by the protoplasm in dif- 

 ferent stages of formation. 



Fig. 9. Section magnified 240 diameters, 

 showing the fibro-vascular bundle with its 

 spiral cell and the cylindrical cells on either 

 side. 



