692 MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS 



A 



or midrib. It is a curious circumstance that when a plant which 

 exhibits the cyclosis is kept in a cold dark place for one or two 

 days, not only is the movement suspended, but the moving particles 

 collect together in little heaps, which are broken up again by the 

 separate motion of their particles when the stimulus of light and 

 warmth occasions a renewal of the activity. It is well to collect the 



specimens about midday, that 

 being the time when the rot at ion 

 is most active, and the IUOM-- 

 meiit is usually quickened In- 

 artificial warmth, which, indeed. 

 is a necessary condition in some 

 instances to its being seen at all. 

 The most convenient method of 

 a]>] living this warmth, while the 

 object is on the stage of the 

 microscope, is to blow a >tivam 

 >f air upon the thin gla^s cover 



FIG. 529. Tissue of the testa or seed-coat 

 of star-anise : A, as seen in section ; 

 B, as seen 011 the surface. 



through 



a glass or metal tube 



previously heated in a spirit- 

 lamp. 



The walls of the cells of 



plants are frequently thickened by deposits, which are first formed 

 on the inner surface, and which may present very different appear- 

 ances according to the manner in which they are arranged. In 



Fie;. .i:(l. Section of cheiTv-stnnr, 

 cutting the cells transversely. 



FlG. ">:!1. Section of eoquilla 

 nut 111 the direction of the 

 lung (liametiT of the cells. 



its simplest e .million such a deposit forms a thin uniform layer 

 over the whole internal surface of 1 lie cellulose wall, scarcely detract- 

 ing at all from its transparency, and chiefly distinguishable bv the 

 'dotted ' appearance which the membrane then presents (fig. 525. A). 

 These dots, however, are not pores, as their aspect might naturally 

 suggest, bu1 are merely points at which the deposit is \\antimr.so 



