FEBRUARY 15, 1901.] 
the Composite. Transverse sections show that 
each element of the mosaic contains chloren- 
chyma, which, though packed densely around 
the edges, forms in the middle a large air- 
chamber, suggesting in appearance the air- 
chambers of certain Hepatice. The leaf, a bi- 
facial one, is maintained in a vertical position. 
In a second paper, Professor Lloyd drew at- 
tention to the occurrence, in Pteris aquilina, of 
nectaries near the bases of the pinnz. The 
activity of these glands reaches a maximum 
during the development of the frond in spring 
and early summer, at which time large drops of 
syrupy nectar exude from the openings, which 
are modified stomata. The object of the speaker 
was to call the attention of teachers of general 
biology to the presence, in a much-used labora- 
tory type, of organs which, though discovered 
by Francis Darwin in 1877, were generally 
overlooked. 
In discussion of Professor Lloyd’s first paper, 
Professor Britton remarked that the author’s 
results were of value as throwing light upon 
the vexed question of the relationship of Chry- 
soma to the golden-rods (Solidago). The two 
groups were probably distinct. It was also re- 
called that the late Dr. Gregory had worked 
extensively upon this problem, but her full re- 
sults had never been published. 
HENRY HE. CRAMPTON, 
Secretary. 
THE ACADEMY OF SCIENCE OF ST. LOUIS. 
AT the meeting of the Academy of Science 
of St. Louis of January 21, 1901, twenty-seven 
persons present, the following subjects were 
presented : 
Rey. M. S. Brennan read a short sketch of 
the progress of astronomy in the United States, 
in which the material equipment and the dis- 
coveries made in that science in this country 
during the past century were passed in review. 
A paper by Professor T. G. Poats, entitled 
‘Isogonic Projection,’ was presented in abstract. 
Professor F. E. Nipher showed by means of 
the lantern a series of negatives printed by 
contact from a lantern slide or positive picture, 
by the light of a 300 candle incandescent lamp. 
The unit of exposure adopted was one lamp- 
meter-second. The exposures varied from 
SCIENCE. 219 
0.0054 to 4,800. All were developed in the 
dark room with hydrochinon, those above 0.f 
exposure having in the bath one drop of satu- 
rated hypo to the ounce of bath. The plate 
having an exposure of 0.1 seemed to be nor- . 
mally exposed. An exposure 210 gave a nega- 
tive showing some fogging, but a print from it 
by ordinary methods gave a very satisfactory 
result. With longer exposures, the plate be 
gan to reverse, locally. With an exposure of 
3,600, which was an exposure of one hour at a 
distance of one meter from a 300-candle lamp, 
half of the plate still showed as a negative. 
The shadow on the gown of a figure in the land- 
scape showed white as a negative, and the part 
of the gown in sunshine showed white as a 
positive. The penumbra between light and 
shadow wasdarker. All the details were sharp, 
but lights and shadows were somewhat incon- 
gruous. With an exposure of 4,800 the details 
had not yet all reversed, but the greater part of 
the plate had become a positive. 
The greatest exposure giving a negative 
which would yield an acceptable print was 210, 
which was 39,000 times the least exposure 
which would give a good negative. All ex- 
posures of 210 and over gave complete posi- 
tives when the plates were developed 1.41 
meter from a 16-candle lamp, or in stronger 
light. As good a picture as has been obtained 
had an exposure of 4,800, and was developed 
within half a meter of a 300-candle lamp. A 
fair picture had even been obtained from a two- 
hour exposure to direct sunlight with a Cramer 
‘Crown’ plate. This plate was developed in a 
perfectly dark room. 
It was stated that hypo in the developing 
bath did not affect the zero condition, or change 
the character as regards positive and negative. 
When no hypo is used, the plate fogs so quickly 
that the picture is invisible, before it has time 
to fully develop. After fixing, the thin shad- 
owy picture showing on the fogged plate has 
the same local positive and negative characters 
that are shown on the clearly defined picture 
of the same exposure, when developed in the 
hypo-hydrochinon bath. 
The greatest exposures giving good results 
that have been measured with reasonable accu- 
racy were about 900,000 times as great as the 
