BOTANY: J. ROSENBAUM 
159 
found to be insensitive to localized currents. This indicates that the 
rheotropic end organs are cutaneous; of these only the tactile corpuscles 
were found to be of significance. This is shown by the following 
experiments. Under normal conditions stimulation of the lips by 
a glass rod produces a very violent negative reaction, and so, too, does 
a current of water of the sort just described. The lips of a normal fish 
were anaesthetized by the application of a 0.1% solution of cocaine. As 
a result the reaction (and assumably the sensitivity) to tactile stimulus 
disappeared completely, and also the reaction to the water current. Not 
only that, biit also the parallelism between the effects of the two sorts 
of stimuli at any instant, both during the gradual benumbing of the 
lips by the reagent and during their progressive recovery from insen- 
sitivity, seemed to be complete. These facts indicate that the end or- 
gans of tactile sensitivity serve also as the essential and organs of rheo- 
tropic sensitivity. Other sensory cells, while they may in some cases 
be affected by currents, apparently play no necessary part in the re- 
action here described. 
^ Contributions from the Bermuda Biological Station for Research, No. 56. 
2 Lyon, E. P., Amer. J. Physiol, Boston, 12, 1904, (149-161). 
3 Parker, G. H., Washington, D. C, Bull. U. S. Fish. Com. for 1902, 1903, (45-64). 
^ Parker, G. H., Amer. Nat., Boston, 37, 1903, (185-204). 
6 Schulze, F. E., Arch. mikr. Anat., Bonn, 6, 1870, (62-88), Taf. 4-6. 
6 Tullberg, T., Vet.-Ak. Bih., Stockholm, 28, 1903, (No. 15, 25 pp.). 
Verworn, Allgemeine Physiologic, 2te Aufl., 1897, (xi + 606). 
STUDIES OF THE GENUS PHYTOPHTHORA 
By J. Rosenbaum 
BUREAU OF PLANT INDUSTRY, WASHINGTON. D. C 
Communicated by R. Pearl, January 10, 1917 
Although the actual number of species of Phytophthora is small, 
geographically they are very widespread, their presence having been 
recorded from the tropics as well as the temperate regions. 
The morphological similarities between the different species, together 
with the great variation in the same species make the identification and 
separations of the species belonging to this genus exceedingly difficult. 
With a view to remedying this situation and determining characters of 
diagnostic value, nine out, of the eleven described species were collected, 
grown in pure culture on artificial media, and studies made from a sys- 
tematic and biometrical standpoint. It was not possible to procure 
material of P. thalictri and P. colocasiae. The following is a list of the 
cultures used: 
