[Illustration: PLATE X.--EXPLANATION OF FIGURES.--1, Spore with thick laminated covering, constant colorless contents, and dark nucleus. B, Part of the wall of cell highly magnified, 0.022 millimeter in thickness. 2, Smaller spore with verruculous covering. 3, Spore with punctulated covering. 4, The same. 5, Minute spores with blue-greenish colored contents, 0.0021 millimeter in diameter. 6, Larger form of 5. 7, Transparent spherical spore, contents distinctly refracting the light, 0.022 millimeter in diameter. 8, Chroococcoid minute cells, with transparent, colorless covering, 0.0041 millimeter in diameter. 9, Biciliated zoospore. 10, Plant of the Gemiasma rubra, thallus on both ends attenuated, composed of seven cells of unequal size. 11, Another complete plant of rectangular shape composed of regularly attached cells. 12, Another complete, irregularly shaped and arranged plant. 13, Another plant, one end with incrassated and regularly arranged cells. 14, Another elliptical shaped plant, the covering on one end attenuated into a long appendix. 15, Three celled plant. 16, Five celled plant. 10-16 magnified 440/1.] I wish to conclude this paper by alluding to some published investigations into the cause of ague, which are interesting, and which I welcome and am thankful for, because all I ask is investigations--not words without investigations. The first the Bartlett following: Dr. John Bartlett is a gentleman of Chicago, of good standing in the profession. In January, 1874, he published in the _Chicago Medical Journal_ a paper on a marsh plant from the Mississippi ague bottoms, supposed to be kindred to the Gemiasmas. In a consideration of its genetic relations to malarious disease, he states that at Keokuk, Iowa, in 1871, near the great ague bottoms of the Mississippi, with Dr. J. P. Safford, he procured a sod containing plants that were as large as rape seeds. He sent specimens of the plants to distinguished botanists, among them M. C. Cook, of London, England. Nothing came of these efforts. 2. In August, 1873, Dr. B. visited Riverside, near Chicago, to hunt up the ague plants. Found none, and also that the ague had existed there from 1871. 3. Lamonot, a town on the Illinois and Michigan Canal, was next visited. A noted ague district. No plants were found, and only two cases of ague, one of foreign origin. Dr. B. here speaks of these plants of Dr. Safford's as causing ague and being different from the Gemiasmas. But he gives no evidence that Safford's plants have been detected in the human habitat. In justice to myself I would like to see this evidence before giving him the place of precedence. 4. Dr. B., Sept. 1, 1873, requested Dr. Safford to search for his plants at East Keokuk. Very few plants and no ague were found where they both were rife in 1871. 5. Later, Sept. 15, 1873, ague was extremely prevalent at East Keokuk, Iowa, where two weeks before no plants were found; they existed more numerously than in 1871.