694 MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS 



peculiar flocculent appearance. This very curious phenomenon may 

 be best observed in the following manner : A very thin trans- 

 verse slice of the seed should first be cut, and laid upon the lower 



glass of the aquatic box ; the cover 

 should then be pressed down, 

 and the box placed upon the 

 stage, so that the microscope may 

 be exactly focussed to the object, 

 the power employed being the 

 1-inch, -inch, or J-inch. The 

 cover of the aquatic box h(in# 

 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 im- 

 mediately looked at. It is im- 

 portant that the slice of the seed 

 should be very thin, for two 

 reasons : first, that the view of 

 the spirals 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. 



In some part or other of most plants we meet with cells contain- 

 ing granules of starch, which specially abound in the tubers of the 

 potato and in the seeds of cereals. Starch-grains are originally 

 formed in the interior of chlorophyll-corpuscles, and therefore within 

 the protoplasm-layer of the cell ; but as they increase in size, the 

 protoplasm-layer thins itself out as a mere covering film, and at last 

 almost entirely disappears. So long as the starch-grains remain 

 imbedded in the protoplasm-layer, they continue to grow ; but when 

 hey accumulate so as to occupy the cell-cavity, their growth stops. 



FIG. 533. Spiral fibres of seed-coat of 

 Collomia. 



FIG. 534. Cells of peony filled 

 with starch. 



FIG. 535. Granules of starch as 

 seen under polarised light. 



They are sometimes minute and very numerous, and so closely 

 packed as to fill the cell-cavity (fig. 534); in other instances they 

 are of much larger dimensions, so that only a comparatively smal 

 number of them are included in any one cell ; while in other 



