218 



THE AMERICAN 



successively to different chemical reactions 

 which effect a destruction of all foreign matters 

 adherent to the membrane in question. 



There is no difficulty in showing you this part 

 of the vegetable cell. Take a potato, cut it, and 

 take from the cut surface a very thin slice on an 

 object-glass ; cover it with a covering glass x^late, 

 and add a drop of water. You will remark on 

 the edges of the slice many cells, in some isarts 

 only a portion, rent, lacerated, and out of con- 

 nection with the adjacent cells. 



If you have any doubt of that being a cellulose 

 membrane, you add some solution of Iodine. 

 Instantly you see the starch in the cell colored a 

 deep blue. The membrane remains transparent, 

 white as before. Add a drop of sulphuric acid 

 and you will see, after a while, the membrane 

 also take a blue hue, but not so intense hy far 

 as the starch bodies near by. The parts near the 

 corner where you let enter the sulphuric acid 

 are colored first, and the color advances gradu- 

 ally in the other direction. 



I made some fine slices of the root of Valeriana 

 officinalis. In putting them between the glass 

 plates I could not distinguish any cellulose mem- 

 brane, or any indication of it. It was because 

 the salts spread through the cells, and the iu- 

 crnstations in their walls rendered the membrane 

 opaque. In boiling the preparation, the water 

 took so much of the soluble salts away that the 

 cellulose membranes could be seen very clearly. 

 This boiling can be performed in any vessel ; but 

 for our purpose it suffices to add some drops of 

 water to the object glass, and hold it for an in- 

 stant over the alcohol lamp. The jumping up 

 and down of the covering glass-plate denotes 

 that there is steam formed, whose expansive 

 power is utilized in the locomotive. 



Now the cellulose membrane is degarnished 

 enough to be observed, and we can try the same 

 experiment with the iodine and sulphuric acid 

 as alluded to before. It is indifferent which of 

 the two yovi add first. I boiled the valerian root 

 in water containing a few drops of sulphuric 

 acid, and the membrane grew free to a greater 

 extent, because the sulphuric acid is a strong- 

 dissolvent for organic as well as for inorganic 

 salts. When you put this slice under the micro- 

 scope, and add a drop or two of iodine solution, 

 you remark easily the growing of the blue color 

 at the margins before white. I tried the same 

 experiment on a fungus which luxuriated npon 

 an animal matter, but with a negative result. A 

 fungus growing in a sugary solution should be 

 carefully washed, because the sugar, being trans- 

 formed by sulpluu-ic acid into dextrine, can take 

 the blue color by adding iodine. The cellular 



membrane of these two vegetables (potato and 

 valerian) is smooth, without any pores. 



The successive coloring of the contents of an 

 integer cell from the side from wliich the reactive 

 comes, demonstrates that it is only b\' the law of 

 Osmose, and not through pores or other holes in 

 the wall that the coloring is eftected. 



We find often at the inside of the cuticle of 

 cellulose, layers of different form, thickness and 

 arrangement. These layers have sometimes the 

 form of a circle, sometimes of a spiral, sometimes 

 of large deposits covering more or less the entire 

 siu-face of the cell. 



When the cell contains one or more rings, it is 

 called the ceWMto [Fig. i as.] 



annulifera, or[ 

 ring-bearing cell.f 

 We find these 1' 

 mixed with spi- 

 rals in a trans- Ti-ansverse cut of Hyacinth leaf . 



verse cut of a leaf of Hyacinth ( Fig. 136). Wlienthe 

 two ends do not grow together, then the layer 

 inside the cell takes the form of a spiral ; this 

 spiral can run from the left to the right, or from 

 the right to the left. The cells . containing the 

 spiral are called fibre cells, when the fibres are 

 clearly separable from the cell wall. A trans- 

 verse cut of Hyacinth shows very distinctly these 

 spirals. And you can also distinguish some 

 fibres running from right to left, and one running 

 in the coiitrary direction. Tlie same can be ob- 

 served in a few cells out of tlie pith of Geranium. 



[Fig. 137.] 



Pith of Geranium 



In this example I had rent the spiral out of the 

 cell, and so I could study it more closely. I found 

 it an elastic substance without hole in the in- 

 terior, the breadth being everywhere the same. 

 In one part I distinguished that the flbre-ribbon 

 was split in the middle (Fig. 137, aa) but soon 

 coming together again, leaving a kind of button- 

 hole. 



In the fibrous cell adjacent (Fig. 137, b) I re- 

 marked that, at the borders of the cell where the 

 flbre-ribbon passed from above to below, there 

 was a little white space (Fig. 137, c), tlie effect 

 of the interference of the light. I followed the 



