PROaRESS OF MICROSCOPICAL SCIENCE. 
267 
one of the mature anthers with the drop of nectar very gently so as to 
leave not more than about a dozen pollen-grains on it, and it is ready 
for examination without even the usual covering of thin glass. If the 
object be examined directly with a quarter-inch object-glass, or even 
a lower power, nothing will be seen but the pollen-grains, but in about 
half an hour a projection like a fleshy root will be seen at the end of 
each grain, and will continue to grow for from one to two hours, at the 
end of which time the pollen-grains and tubes will resemble in appear- 
ance very long snakes, the grain representing the head. The sap may 
also be seen running down one side of the tube, turning at the point, 
and returning on the other side. When prepared in this manner the 
object is perfect, and being free from foreign matter is clear and 
beautiful. In preparing the objects care should be taken not to place 
them in too warm or too dry a place, as the continuous growth of the 
pollen-tubes entirely depends on the length of time that the nectar 
remains in a sufficiently fluid state. The student must not be dis- 
couraged if he fails a few times, as he will be amply rewarded when 
he secures a good specimen, which may be made a permanent one 
without any further trouble than that of placing a piece of thin micro- 
scopic glass over it while the nectar is in a fluid state, and carefully 
pressing it down to eject the air-bubbles. The nectar will soon 
harden, and the pollen-tubes be preserved in a perfectly transparent 
vehicle ; prepared in this manner, I have a perfect specimen a year 
old. We may take it for granted that any flower which produces 
nectar in sufficient quantity will produce the tubes in the manner 
described ; but I have been more successful with bulbous plants than 
any others, having obtained some beautiful objecLs from different 
varieties of Hymenocallis (Pancratium), Crinum, &c. The foregoing 
is a simple and successful means of accomplishing a delicate opera- 
tion, which most botanical students, who in these days are invariably 
workers with the microscope, will be glad to know." 
The Minute Anatomy of the Bog's Skin. — This subject has been 
thoroughly investigated by Dr. W. Stirling, who has published a most 
valuable paper on the subject in the Reports of the ' Saxon Academy 
of Sciences ' for 1875. He says that the skin to be examined was 
stretched over a glass ring and digested in artificial gastric juice, pre- 
pared by adding 0*2 per cent, of hydrochloric acid to carefully 
prepared glycerine-pepsine. The temperature was maintained at 38° 
to 40° Cent. (100-4:° to 104° Fahr.). The fluid was renewed every 
two hours, and digestion was generally sufficiently advanced in four to 
six hours. The skin, still on the ring, was then washed with water, 
and placed in distilled water for twenty-four hours. During the time 
it had swelled to four to six times its thickness, and was in a suit- 
able condition for making sections which could be examined at once, 
or after being stained. The leg was injected with a clear watery solu- 
tion of Berlin blue from the femoral artery, with a pressure of 100 to 
200 millimeters of mercury, a cord being screwed tightly round the 
limb above the point of injection. The solution was allowed to flow 
into the vessel as long as it would go — usually for a period of many 
hours. By this process the vessels were filled with the blue, whilst 
