XIII. NOTES ON SOME SPECIES OF GYMNOSPORANGIUM AND CHRYSOMYXA OF THE UNITED STATES. By W. G. FARLOW. Communicated February 11th, 1885. In a paper published in the Anniversary Memoirs of the Boston Society of Natural History in 1880, I gave an account of my attempts to show, by means of cultures, the relationship of the Gymnosporangia found near Boston to the different forms of Rastelia occurring in the same region; and also, by reviewing the geographical distribution of the species of both genera in the United States, to ascertain the probabilities of the genetic connection of different forms of the genera in question. My cultures, however, were not successful in proving the direct relationship of any given Gymnosporangium with any given Ræstelia; but, as the subject is of importance, both from a biological and practical standpoint, I have made further attempts to see whether a more definite result could be reached. Specimens of The method of culture employed was the following. different species of Gymnosporangium were gathered early in May, before the spores had begun to germinate, and while the spore masses were flat and not swollen in gelatinous protuberances, as is the case when they are moistened by showers. The specimens were then placed in watch-glasses under moistened glasses, each species by itself, when the spore masses soon expanded, and the spores began to germinate. It was in this way easy to arrange so that the spores of the different species were kept pure, a fact confirmed by microscopic examination. As the spores germinated, the sporidia, of a bright orange color, dropped into the moist watch-glasses, and were used at once for infecting the desired plants. Two kinds of material were used. The first consisted of leaves of different Pomacea, which were freshly gathered in the Botanic Garden of Cambridge, and at a distance from any species of Juniperus which could have been infested by a Gymnosporangium. The leaves were placed on moistened glass slides and arranged on zinc stands under bell-glasses. The sporidia were then carefully dropped upon the leaves, which were immediately covered by a bell-glass. The leaves under each glass were sown with the sporidia of but one species, and subsequently, when it was necessary to remoisten the slides, the bell-glasses were removed for a moment only, and at no time were the leaves under more than one bell-glass exposed. I also used a number of small seedlings of Pomacea, each pot being covered by a glass receiver. The seedlings were supposed to be in a healthy condition, but, to serve as a check, a number of similar seedlings were kept on which no sporidia were sown. The young plants were inoculated, either by dropping the sporidia upon them, or, in cases where the leaves were not in such a position as to retain drops well, small pieces of the gelatinous spore-masses were placed on them, it first being ascertained that the spores had begun to germinate. After three or four days it was necessary to remove the remains of the gelatinous masses in order to prevent moulding. After the lapse of a week, at which period the germinal tubes, if ever, must have made their way into the leaves, I attempted in a few cases to remove the glass receivers and continue the cultures in the open air. This, however, was impossible, for the plants wilted to such an extent that I was obliged to keep them constantly covered. European experimenters usually expose their cultures to the air after a few days, but it is doubtful whether this can be done in our climate except in the most favorable cases, so great and sudden are the changes of moisture and temperature. The following statement shows the results of the cultures made in May and June, 1883. I was unable to continue my cultures, unfortunately, in the spring of 1884, as I had intended. The names of the species with which experiments were made are those given in my paper above mentioned, in which the synonymy is given. I. GYM. FUSCUM var. GLOBOSUM. May 18. Sporidia sown on May 26. 5 seedlings of apple. 3 leaves of Crataegus oxyacantha. 3 leaves of apple. 4 leaves of Amelanchier Canadensis. Spermogonia appeared on four of the apple seedlings. May 28. Spermogonia appeared on the remaining apple seedling, and very abundantly on the three leaves of Cratagus. June 1. Spermogonia appeared on one leaf of apple. June 8. The spermogonia on leaves named still visible, but the leaves had become so mouldy that there was no hope of the development of acidia, and the cultures were abandoned. II. GYM. MACROPUS. May 18. Sporidia sown on 5 seedlings of apple. 4 leaves of apple. 3 leaves of Amelanchier Canadensis. 3 leaves of Crataegus oxyacantha. May 28. Soon after the sowing, the leaves of apple seedlings became mottled, but no spermogonia were plainly seen until the 28th, when they appeared on all the five seedlings. June 8. Culture abandoned, as the leaves were all mouldy. III. GYM. CLAVIPES. May 18. Sporidia sown on 5 seedlings of apple. 4 leaves of apple. 4 leaves of Amelanchier Canadensis. 3 leaves of Crataegus oxyacantha. May 23. May 24. May 26. May 28. June 10. Spermogonia on two more leaves of Amelanchier. IV. GYM. BISEPTATUM. May 19. Sporidia sown on May 28. June 5. 5 seedlings of apple. 3 leaves of apple. 4 leaves of Amelanchier Canadensis. 3 leaves of Crataegus oxycantha. Spermogonia appeared on three Amelanchier leaves. V. GYM. ELLISII. May 23. Sporidia sown on two seedlings of apple. May 29. As the previous sowing produced no result, owing possibly to the sporidia not being sufficiently abundant, five seedlings of apple, including the two mentioned above, were sown with fresh material. No result. Comments on Cultures I.-V. - The cultures I.-III. were started on the same day. No. IV. was not started until the following day, as a microscopic examination showed that the spores were not germinating freely until May 19th. In No. V. the sporidia were not produced in sufficient quantity for sowing until May 23d, and even then they were scanty, so that fresh specimens were collected, which produced a sufficient quantity of sporidia for sowing on May 29th. At the time when the five cultures were started, the only seedlings of a suitable size which could be procured were those of apple; but as it was easier to obtain pure spores of the species of Gymnosporangium on the date named, the cultures were then started, and a second series of cultures were arranged later, when other seedlings could be procured. The spores for the second series were from specimens selected with care, so as to be as pure as possible; but from the later date, and the fact that there had been showers which had swollen the masses of spores, the possibility of the accidental mixture of the spores of one species with those of another could not be guarded against with the same degree of certainty as in the preceding series. It may be remarked that in 1883 the season was backward, and the Gymnosporangia did not mature as early as they frequently do. In both series of cultures the control plants remained free from spermogonia. Where the statement is above made, that the cultures were abandoned on a given day, it should be understood that the statement applies only to the leaves under bellglasses. In the cases where spermogonia appeared on the leaves of seedlings, the cultures were kept for a longer period; but these cases will be referred to again later. VI. GYM. FUSCUM var. GLOBOSUM. May 25. Sporidia sown on 2 seedlings of Crataegus Douglasii. 1 seedling of Pyrus sp. cult. May 31. Spermogonia appeared on all the seedlings. VII. GYM. MACROPUS. May 25. Sporidia sown on 2 seedlings of Crataegus Douglasii. 1 seedling of Pyrus cult. June 5. Spermogonia appeared on one Crataegus. VIII. GYM. CLAVIPES. May 25. Sporidia sown on 1 seedling of Crataegus Douglasii. 1 seedling of Pyrus cult. May 31. Spermogonia appeared on seedling of Pyrus. A third set of experiments consisted in placing fresh shoots of Amelanchier Canadensis and Pyrus arbutifolia in jars of water, covering them with receivers, and sowing on the leaves the sporidia of G. macropus, G. clavipes, G. biseptatum, and G. Ellisii. The cultures were started on May 30th, with the following result. On June 4th, spermogonia appeared on both Amelanchier and Pyrus arbutifolia sown with the sporidia of G. macropus and G. clavipes, and on Amelanchier sown with G. biseptatum. As the sporidia of G. biseptatum and G. Ellisii proved more refractory than those of other species, two supplementary cultures were made, as follows: — GYM. BISEPTATUM. May 29. Sporidia sown on 5 leaves of Pyrus arbutifolia. 3 leaves of Nesæa verticillata. Young shoots of Nesæa, Amelanchier, and Pyrus arbutifolia. May 31. Spermogonia appeared on leaves of Amelanchier shoot. May 29. Sporidia sown on GYM. ELLISII. 5 leaves of Pyrus arbutifolia. 3 leaves of Nesæa verticillata. Young shoots of Pyrus arbutifolia and Nesaa. No spermogonia. In these last two cultures I was led to try the leaves of Pyrus arbutifolia because the form known as Ræstelid transformans had been usually found by me in districts near Cupressus thyoides, on which G. biseptatum and G. Ellisii are parasitic. As I had never succeeded in getting spermogonia from sowings of G. Ellisii on Pomacea, it occurred to me that possibly the acidial form of that species might be found on a host of some other order, and, in the cedar swamps where G. Ellisii is found, Nesaa abounds and is not infrequently infested with the |