Vegetable Productions. 83 



dantly in the rivers of the south of Europe, but is not 

 a native of this country ; it may, however, be readily 

 grown in a large glass jar with a little mould at the 

 bottom, No. 8 (a) . Its long grass-like leaves are too 

 thick to allow the transmission of sufficient light 

 without some special preparation. It is, therefore, 

 requisite to make with a sharp knife a thin slice 

 or shaving of the leaf, not of the outer surface, 

 but of that next to it ; and this must be placed in a 

 little water in the live-box. A power of 200 dia- 

 meters should be used. The whole field of view will 

 then appear occupied by cells similar to the small 

 number figured at No. 8 (6), with bright green par- 

 ticles revolving in each, in a steady and regular motion, 

 strictly limited to the boundary of each cell. It some- 

 times happens that the slicing operation will have put 

 a temporary stop to the rotation ; but a slight 

 warming of the live-box will quickly cause it; to re- 

 commence. 



Spiral fibre. A substance often deposited in the 

 interior of cells, tightly coiled up till a little moisture 

 applied causes it to uncoil suddenly. It can be very 

 curiously shown by cutting a thin and small slice off 

 the outside of a collomia seed, and placing it in the 

 live-box of the microscope, with a magnifying power 

 of about sixty diameters. The cover of the live-box 

 should be placed over it at first without water, that 

 the focus may be nicely arranged. Then the cover is 

 to be lifted up, a small drop of water put on its 

 under surface, and this pressed down over the slice 

 of seed. This being done, the spirals will spring 



