of General Notes. January, 
though quite obliterated by a reflection from its whole surface, to the 
availability of light at the polarizing angle as compared with vertical 
rays; but in fact the instrument does not furnish a vertical illumina- 
tion in any case, and when all light is stopped off except from its 
‘ marginal portion an equally complete polarization is effected without, 
in common practice as well as in theory, the advantages attained by a 
unilateral illumination from one edge only of the reflector. In applying 
the same law to the use of transmitted light for transparent objects, it is 
advised to place the lamp in such a position that its rays shall fall upon 
the mirror at an angle of about 54}° in order that the reflected and 
refracted rays may be as perfectly separated as possible. To obtain the 
angle accurately in all these cases, it is advised to set the illuminating 
apparatus by the aid of a sector or a properly divided card. The em- 
ployment of the silvered side reflector below the object, as a means of 
transparent or of dark ground illumination, is mentioned as giving a clear 
soft light and excellent definition at any desired angle of incidence, no 
claim being made that its use should be limited to any special angle; a 
judgment in which all who have been accustomed to use this little in- 
strument as a substage accessory will be likely to cordially concur. 
PoLLeN Tuses ror tHe Microscope. — Mr. J. O’Brien’s remarks 
on this subject, quoted from the Garden by the Monthly Microscopical 
Journal, represent that he always failed to succeed in obtaining pollen 
tubes by dissecting the fertilizing stigmas, though spending much time 
in the effort, and that he had always seen similar failure attend the - 
labors of others. He therefore recommends that the tubes be obtained 
on a slide by means of the nectar which appears on the stigma at the 
time of fertilization. The centre of a common microscope slide is 
touched to the drop of nectar on the stigma, care having been taken to 
prevent previous pillage by insects, and the spot of nectar thus obtained 
on the slide is touched by a mature anther so as to leave a few pollen 
grains on it. In about half an hour a projection like a fleshy root may 
be seen to grow from the end of each pollen grain; and after an hour or 
two each tube will be long and snake-like, the grain still attached and 
representing the head. The rotation of the contents of the tube may 
now be observed, the fluid passing down one side of the tube and re- 
rning on the other side. Temperature and moisture should be care- 
fall controlled, as the growth depends on the fluid condition of the 
tar. When sufficiently developed the object may be immediately 
mounted by pressing down upon it a cover glass, the nectar soon hard- 
ening and forming a mounting material in which the pollen is well 
` shown. Specimens prepared in this manner a year ago are still per- : 
fectly preserved. The author presumes that any plant which produces 
the nectar in sufficient quantity may be treated in this way, though he 
has succeeded best with bulbous plants, Lilium, Hymenocallis (Panera- 
tium), Crinum, ete. It would be an interesting and useful field ‘for in- 
a eh ee, 
