40 A HALF-HOUR WITH THE 



circumstances the sugar crystal loses its definite 

 outline, and assumes the form seen at figure 240. 



The external surface of the parts of all plants 

 will aflTord a rich field of amusement and instruc- 

 tion to the microscopic observer. The cuticle, or 

 epidermis, of which we have before spoken, has a 

 very varied structure, and contains the little open- 

 ings (stomates) before described. The cuticle, which, 

 in a large number of cases, is smooth, becomes 

 elevated in some instances, and forms a series of 

 projections, which, according to their form, are 

 called " papillae," " warts," " hairs," " glands," and 

 " prickles." The papillae are slight elevations, con- 

 sisting of one, two, or more cells ; the warts are 

 larger and harder ; whilst the hairs are long, the 

 glands contain a secretion, and the prickles are 

 hard and sharp. For examining the form and 

 growth of these hairs, the flowers of the common 

 pansy (heart's-ease) afford a good object. Some of 

 the projections are merely papillae, as in the case 

 of the kind of rudimentary hair rejDresented in 

 figure 75, plate 3 j others are found longer, and 

 more like hairs, as seen in figure 76; whilst others 

 are long, and, the sides of the hair having contracted, 

 they assume the appearance of a knotted stick, as 

 seen in the hair from the throat of the flower of the 

 pansy, at figure 78. The family of grasses, wheat, 

 barley, oats, and other forms, are favourable sub- 

 jects for the examination of simple hairs, or hairs 

 composed of a single elongated cell. At figure 74, 

 a single hair is given from a common grass. All 

 that is necessary to be done, in order to see these 

 hairs, is to take any part of the plant where they 

 are present, and to slice off a small portion with a 

 sharp penknife or razor, and place it under the 

 Microscope. They may be either examined dry, or 

 a little water may be added, and a piece of thin 



