398 



SPIRAL CELLS. — STARCH-GRANULES. 



named Saccolabium gultatum, the Spiral Cells are unusually long, 

 and have spires winding in opposite directions ; so that, by their 

 mutual intersection, a series of diamond-shaped markings is pro- 

 duced. Spiral cells are often found upon the surface of the testa 

 or outer coat of Seeds ; and in the CoUomia grandiflora, the 

 Salvia verbenaca (Wild Clary), and some other plants, the mem- 

 brane of these cells is so weak, and the elasticity of their fibres so 

 great, that when the membrane is softened by the action of Water, 

 the fibres suddenly uncoil and elongate themselves (Fig. 207), 

 springing out, as it were, from the surface of the Seed, to which 

 they give a peculiar flocculent appearance. This very curious 

 phenomenon, which is not unfrequently spoken of by persons 

 ignorant of its true nature as the Germination of the Seed, may be 

 best observed in the following manner : — A very thin transverse 

 slice of the Seed should first be cut, and laid upon tne lower glass 

 of the Aquatic-box ; the cover should then be pressed down, and 

 the box placed upon the Stage, so that the body of the microscope 

 may be exactly focussed to the object, the power employed being 

 the 1-inch, 2-3rds inch, or the ^ inch objective. The cover of the 

 Aquatic-box being then removed, a small drop of water should be 

 placed on that part of its internal surface with which the slice of 

 the seed had been in contact ; and the cover being replaced, the 

 object should be immediately looked at. It is important that the 

 slice of the Seed should be very thin, for two reasons ; first, that 

 the view of the spires may not be confused by their aggregation in 

 too great numbers ; and second, that the drop of water should be 

 held in its place by capillary attraction, instead of running down 

 and leaving the object, as it will do if the glasses be too widely 

 separated. 



292. In some part or other of most Plants we meet with Cells 

 containing granules of Starch. These granules are sometimes 

 minute and very numerous, and are so closely packed together as 

 to fill the cavity (Fig. 208) ; in other instances they are of much 



larger dimensions, so 

 Fig. 208. that only a small num- 



ber of them can be in- 

 cluded in any one Cell; 

 while in other cases, 

 again, they are both 

 few and minute, so that 

 they form but a small 

 proportion of the cell- 

 contents. Their nature is 

 at once detected by the 

 addition of a solution 

 of Iodine, which gives 

 them a beautiful blue 

 colour. Each granule exhibits a peculiar spot, termed the Hilum, 

 which marks the point at which, in its early state, it is attached to 



Cells of Pieony, filled with Starch. 



