No incrustation found. Examined the vegetation found on the margin of the Ridge Hills Farm pond. Among other things I found an Anguillula fluviatilis. Abundance of microspores, bacteria. Some of the Protococci. Gelatinous masses, allied to the protuberans, of a light yellow color scattered all over with well developed spores, larger than those found in the Protuberans. One or two oval sporanges with double outlines. This observation was repeated, but the specimens were not so rich. Another specimen from the same locality was shown to be made up of mosses by the venation of leaves.
Mine host with whom I lodged had a microscopical mount of the Protococcus nivalis in excellent state of preservation. The sporangia were very red and beautiful, but they showed no double cell wall.
In this locality ague is unknown; indeed, the place is one of unusual salubrity. It is interesting to note here to show how some of the algæ are diffused. I found here an artificial pond fed by a spring, and subject to overflow from another pond in spring and winter. A stream of living water as large as one's arm (adult) feeds this artificial pond, still it was crowded with the Clathrocyotis æruginosa of some writers and the Polycoccus of Reinsch. How it got there has not yet been explained.
The migration of the ague eastward is a matter of great interest; it is to be hoped that the localities may be searched carefully for your plants, as I did in New Haven.
In this connection I desire to say something about the presence of the Gemiasmas in the Croton water. The record I have given of finding the Gemiasma verdans is not a solitary instance. I did not find the gemiasmas in the Cochituate, nor generally in the drinking waters of over thirty different municipalities or towns I have examined during several years past. I have no difficulty in accounting for the presence of the Gemiasmas in the Croton, as during the last summer I made studies of the Gemiasma at Washington Heights, near 165th St. and 10th Ave., N.Y.
Plate VIII. is a photograph of a drawing of some of the Gemiasmas projected by the sun on the wall and sketched by the artist on the wall, putting the details in from microscopical specimens, viewed in the ordinary way. This should make the subject of another observation.
I visited this locality several times during August and October, 1881. I found an abundance of the saline incrustation of which you have spoken, and at the time of my first visit there was a little pond hole just east of the point named that was in the act of drying up. Finally it dried completely up, and then the saline and green incrustations both were abundant enough. The only species, however, I found of the ague plants was the Gemiasma verdans. On two occasions of a visit with my pupils I demonstrated the presence of the plants in the nasal excretions from my nostrils. I had been sneezing somewhat.
There is one circumstance I would like to mention here: that was, that when, for convenience' sake, my visits were made late in the day, I did not find the plants abundant, still could always get enough to demonstrate their presence; but when my visits were timed so as to come in the early morning, when the dew was on, there was no difficulty whatever in finding multitudes of beautiful and well developed plants.
To my mind this is a conclusive corroboration of your own statements in which you speak of the plants bursting, and being dissipated by the heat of the summer sun, and the disseminated spores accumulating in aggregations so as to form the white incrustation in connection with saline bodies which you have so often pointed out.
I also have repeated your experiments in relation to the collection of the mud, turf, sods, etc., and have known them to be carried many hundred miles off and identified. I have also found the little depressions caused by the tread of cattle affording a fine nidus for the plants. You have only to scrape the minutest point off with a needle or tooth pick to find an abundance by examination. I have not been able to explore many other sites, nor do I care, as I found all the materials I sought in the vicinity of New York.