The Microscope. 119 



Acknowledgments. — From Prof. Wm. A. Rogers, Waterville, 

 Me., we have received several slides of his exquisite rulings, and eye- 

 piece and stage micrometers; from Prof. Henry Mills, Buffalo, six 

 interesting sponge mounts ; from W. H. Curtis, Haverhill, Mass., a 

 slide of diatoms on alg?e from Pacific coast. Dr. George W. Rafter, 

 Rochester, has our apologies for tardy acknowledgment of three 

 photographs Pleurosigma, illustrating his paper or the use of the 

 Amplifier in Photo-micrography. These were taken with Bausch & 

 Lomb's objectives ^ inch and ^ inch, student and first-class series 

 respectively. The results are exceedingly beautiful. 



TECHNOLOGY. 



A Correction. — The alcohol in Mayer's carmine, the formula 

 for which was given in our March number, should be 85 per cent, 

 instead of 8 per cent., as printed. 



Staining Living Vegetable Tissues. — If a fresh, green stem is 

 cut from a plant, and the newly-cut end be placed in a solution of 

 any of the substances commonly used for staining, this coloring- 

 matter will gradually be absorbed in the process of circulation, and 

 be distributed through the tissues. Select a plant with the leaves 

 sufficiently translucent to admit of examination by transmitted light 

 under low powers. Cut off a small branch and place the end of the 

 «tem in a bottle or other vessel containing the coloring solution. 

 Place the vessel conveniently near the microscope, so that one of the 

 leaves of the cutting may be laid out over the stage, as is done with the 

 foot of a frog in the examination of its circulation. Then watch the 

 absorption of the coloring-matter as it passes from cell to cell. 



In selecting specimens for use in this experiment the newest 

 shoots will be fouad most satisfactory, because the absorption of the 

 coloring-matter is more rapid, and, consequently, more easily 

 watched. As the preparation is not a permanent one, it is unneces- 

 sary to give it the careful preliminary treatment required in mounting. 



Some coloring-matters are more readily absorbed by the living 

 plant than others. The various coal-tar derivatives are taken up 

 very slowly, and so are the ordinary carmine and cochineal if simply 

 dissolved in water. The most satisfactory, simply because they are the 

 most rapid, are the colored writing- fluids of commerce, more especially 

 the scarlet and purple. With some of these the leaf is thoroughly 

 stained in the course of fifteen minutes, making a beautiful object 

 even to the naked eye. 



