FOOD RESERVES IN THE PEA. 29 



rone grains also have increased in size, and appear as if porous or 

 even hollow. We recognise, therefore, in iodine green and methyl 

 green reagents which in the present case constitute specific stains 

 for nuclear substance. Simultaneously, it is true, the cell-walls 

 also colour somewhat, but this does not diminish the value of 

 these dyes as reagents for nuclear staining. The cell-walls appear 

 of a beautiful bright-blue colour, and, as the result of this, are 

 traced out in the glycerine preparations much more readily than 

 before. The intercellular spaces also stand out more sharply. 

 The figure becomes still more beautiful if to watery iodine-green 

 solution we add a little fuchsin (magenta) until the previously 

 blue colour becomes distinctly violet, and then treat the section 

 with the mixture. As before the nucleus and cell-wall stain a 

 beautiful blue, but the aleurone grains and ground substance 

 a deep red. If a small drop of this double stain be mixed on the 

 slide with a large drop of glycerine, and the section then laid in 

 it, the staining proceeds as above but much more feebly ; the 

 aleurone grains, however, by way of compensation, are not 

 injured in the reaction. 



In the brown reaction with iodine, the accumulation of stains, 

 and the brick-red colour from Millon's reagent, we have become 

 acquainted with the most important means whereby to recognise 

 under the microscope albuminous bodies ; for to these belong 

 aleurone grains as well as cytoplasm and nucleus. The substance 

 of the nucleus shows a specially strong affinity for certain stains. 

 The constituents of protoplasm (cytoplasm, nucleus, chroma- 

 tophores), are, however, in general only feebly stained when in the 

 living state, and that only by certain stains; a notable accumula- 

 tion of colour only occurs after death, though in many cases 

 death may be brought about by the influence of the stain itself or 

 of the medium in which it is dissolved. Aleurone grains, which 

 are composed of inactive protein matter, take the stain with pro- 

 portional rapidity. These aleurone grains consist chiefly of 

 vitellin. 



Endosperm of Wheat. A grain of wheat (Triticum vulgare) 

 can be recommended as a second object of study. The grain is 

 first halved (across) with a pocket-knife,, then the half fixed in a 

 small hand-vice in order to have sections taken from it. This 

 time it is desirable so to take the sections that a piece of the skin 

 also is present on them. Before cutting, moisten the surface 

 with glycerine,, and observe the section in the same fluid (Fig. 12). 



