MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS. 383 



ilium), of which a small portion is represented in Fig. 276. The dif- 

 ferent portions of this petal when it has been dried after stripping it of 

 its epiderm, immersed for an hour or two in oil of turpentine, and then 

 mounted in Canada balsam exhibit a most beautiful variety of vivid 

 coloration, which is seen to exist chiefly in the thickened partitions of 

 the cells; whilst the surface of each cell presents a very curious opaque 

 spot with numerous diverging prolongations. This method of prepara- 

 tion, however, does not give a true idea of the structure of the cells; for 

 each of them has a peculiar mammillary protuberance, the base of which 

 is surrounded by hairs; and this it is 



which gives the velvety appearance Fie, 276^ 



to the surface of the petal, and 

 which, when altered by drying and 

 compression, occasions the* peculiar 

 spots represented in Fig. 276. Their 

 real character may be brought into 

 view by Dr. Inmaii's method; which 

 consists in drying the petal (when 

 stripped of its epiderm) on a slip of 

 glass, to which it adheres, and then 

 placing on it a little Canada balsam 

 diluted with Turpentine, which is to 

 be boiled for an instant over the 

 spirit-lamp, after which it is to be Cells **$%$&. T nium 



covered with a thin glass. The boil- 

 ing ' blisters ' it, but does not remove the color; and on examination many 

 of the cells will be found showing the mammilla very distinctly, with a 

 score of hairs surrounding its base, each of these slightly curved, and 

 pointing towards the apex of the mammilla. The petal of the common 

 Scarlet Pimpernel (Anagallis arvensis), that of the common Chick-weed 

 (Stellaria media), together with many others of a small and delicate 

 character, are also very beautiful microscopic objects; and the two just 

 named are peculiarly favorable subjects for the examination of the spiral 

 vessels in their natural position. For the 'veins' which traverse these 

 petals are entirely made-up of spiral vessels, none of which individually 

 attain any great length; but one follows or takes the place of another, the 

 conical commencement of each somewhat overlapping the like termina- 

 tion of its predecessor; and where the 'veins' seem to branch, this does, 

 not happen by the bifurcation of a spiral vessel, but by the 'splicing-on' 

 (so to speak) of one to the side of another, or of two new vessels diverg- 

 ing from one another to the end of that which formed the principal vein. 

 386. The anthers mud. pollen-grains, also, present numerous objects of 

 great interest, both to the scientific Botanist and to the amateur Micro- 

 scopist. In the first place, they afford a good opportunity of study- 

 ing that form of 'free' cell-development which seems peculiar to the 

 parts concerned in the reproductive process, and which consists in the 

 development of a new cell-wall round an isolated mass of protoplasm 

 forming part of the contents of a 'parent-cell;' so that the new cell lies 

 free within its cavity, instead of being formed by its subdivision, as in the 

 ordinary method of multiplication ( 226). If the anther be examined 

 by thin sections at an early stage of its development within the young 

 flower-bud, it will be found to be made-up of ordinary cellular parenchyma 

 in which no peculiarity any where shows itself: but a gradual 'differentia- 

 tion' speedily takes place, consisting in the development of a set of a very 



