170 
the Biological Section, Prof. Arthur resigned and Dr. N. L. Brit- 
ton was elected in his place. 
A letter was read from Dr. Asa Gray, conveying a revision 
of the genus Dodecatheon, in which he recognizes five species, 
differing in this from his conclusion, in the last edition of Vol. ii, 
Syn. Flor. N. A., where all the forms were considered as varieties 
of D. Meadia. The present classification is based on characters 
of the capsules. 
Prof. E. W. Claypole presented some notes on the action of 
the Potato Rot fungus (Peronospora infestaus) on the tubers, stat- 
ing that the mycelium enters at the eyes, where the vascular 
system reaches the surface, penetrates and destroys it, but leaves 
the starch-cells intact. Subsequently Bacterium termo attacks 
the latter. The so-called “resting-spores” of Peronospora were 
shown under the microscope. 
Prof. F. Lamson Scribner described and illustrated his method 
of making drawings of minute portions of plants. The apparatus 
used consists of a Zentmayer dissecting microscope, with the 
metal base replaced by a wooden one, which slides in a frame 
hinged to a heavy base board. When in use, the frame is placed 
vertically and the focal distance adjusted as desired. A Wollas- 
ton camera and an adaptor for lenses are attached; drawings are 
made on tracing paper and transferred by means of a steel point 
to Bristol board. The final lines are inked with Keuffel & Es- 
ser’s pen No. 1459. Remarks were made by Prof. Burrill and. 
Dr. Beal. 
Dr. W. J. Beal exhibited a cheap and convenient tray to con- 
tain the apparatus used by students in laboratory work, and in- 
vited criticism. Dr. Farlow remarked on the danger to lenses 
from the proximity of reagents. Prof.’J. H. Pillsbury advocated 
the use of a board with holes and grooves. 
W. H. Seaman read a paper on the occurrence of Marsilea 
quadrifolia in the fish ponds at Washington. (See BULLETIN, 
xiii, p. 144.) Dr. Beal stated that it had spread extensively in 
Michigan. Rev. Thos. Monong said that it was: now abundant 
in Concord River, Mass., extending along its banks for miles, to 
the exclusion of other aquatic plants, being almost as objection- 
able as Anacharis is in Europe. It all appears to have originated 
