J. C. Arthur

Uredinales of Porto Rico based on collections by H H Whetzel and E W Olive.

A botanical expedition was made to Porto Rico in the spring of I916 by Professor H. H. Whetzel, of Cornell University, and Dr. E. W. Olive, of the Brooklyn Botanic Garden. They reached the island on February 23, and left it on April 26, permitting thus about two months of uninterrupted work. All kinds of plants were collected, but especial attention was given to fungi, and a generous portion to the Uredinales. As a result of their labors 383 numbered collections of Uredinales were secured and shortly afterward submitted to the writer for study. The 383 collections were found to represent I22 species, as now understood, and these are systematically treated in the following pages. The writer and the scientific public are under large obligation to the collectors for their assiduous and painstaking labors, and for their generosity in turning over to another the whole set for unreserved examination and record.

Cultures of Uredineae in 1911

The following is a complete list of the successful cultures made during the year 1911. It is divided into two series, species that have previously been grown in cultures and reported by the writer ...

Terminology of the Spore-Structures in the Uredinales

SOME time ago I began to study groups of species among the rusts in a more methodical way than usually pursued, and as part of the method undertook to prepare uniform descriptions in which like parts of each structure should receive the same kind of treatment in every case. I. soon met with an. obstacle that had not been anticipated. The terminology in use was found to be clumsy, ambiguous, poorly correlated, and quite inadequate to show homologies properly. I will illustrate a few of the difficulties which confronted me. When an aecidium is mentioned, there is a tolerably clear conception of a cuplike structure filled with spores; but when one reaches the next stage of the rust, what is the meaning conveyed by the word uredo ? I think it is most generally employed as a collective term, referring to the second stage of the rust. We can properly say that the uredo occurs on leaves of a certain host, but if we wish to specify a single uredinial structure corresponding to an aecidium, it is necessary to say uredosorus; and yet it is not permissible to say aecidiosorus. Passing to the third stage of the rust there appears to be neither a specific nor a collective name with which to designate it. The nearest approach to a specific term analogous to aecidium is teleutosorus, and to a collective term analogous to uredo is teleutostage. We can say properly that aecidia appeared on a leaf, after a time they were followed by the uredo, and finally the teleutospore stage was developed; in which statement we have used three different methods to express the same idea relative to similar spore-structures. Taking up the first stage again, there appears to be nothing inappropriate in calling the single spore-structure an aecidium so long as we have in mind the first stage of species belonging to the genus Puccinia or Uromyces; but in the genus Phragmidium there is no peridium present, and in Gymnoconia not only is the peridium absent but the spore-layer is extended and indefinite, and the term aecidium now seems far less applicable. For such cases it is customary to call the structure a caeoma, instead of an

Fern rusts and their aecia

The rusts in general, a well circumscribed and readily recognized group of parasitic fungi, have not yet been assorted under any generally accepted classification, although the process of placing them in genera, families, orders, etc., has been actively proceeding for considerably over a hundred years. There are more than a thousand species of rusts in North America under about eighty genera. So great is the disparity in views between the most capable and advanced thinkers that there is no unanimity regarding what forms may be taken to represent primitive or ancient states, and what the most recent, specialized states. It is the situation the phanerogamic botanists were in before it was decided whether the cone-bearing plants (gymnosperms) were more suitably placed before all other flowering plants, in the middle, or at the end of the series. So long as the mycologists can not agree whether a short cycled form, like Puccinia Xanthii with its single stage and one kind of spores, is representative of rusts in their primitive condition in early geologic times, or a long cycled form, like Puccinia graminis with its several stages and diversity of spores, there is no hope for an acceptable classification of the rusts. If one were so blind as to be unable to tell which was the

Uredinales of Porto Rico Based on Collections by F. L. Stevens

76. Aecidium abscedens sp. nov. Pycnia epiphyllous, numerous on brownish spots 4-9 mm. across, prominent, golden-yellow becoming dark-brown, hemispheric, subcuticular, I40-200 u broad by about half as high. Aecia hypophyllous, numerous in crowded groups, cupulate; peridia short, cylindric, o.I-o.3 mm. in diameter, soon open, coarsely lacerate, somewhat revolute, peridial cells colorless, somewhat overlapping, oblong, 11-I6 by 20-371, the outer wall I.5-3,U thick, smooth, the inner wall slightly thicker, moderately verrucose; aeciospores broadly ellipsoid or globoid, I8-2I by 20-27/u wall pale-yellow, thin, I-1.5 U, very closely and finely verrucose.

Cultures of Uredineae in 1910

The present article is the eleventh of a series of reports1 by the writer upon the culture of plant rusts, beginning in I899. Almost uniform progress has been made during the twelve years in the prime purpose of the work, that of experimentally connecting the sporophytic and gametophytic phases of heteroecious rusts, as well as the study of autoecious species and in some cases the detection of races. The work of the year is representative in these several respects. It was under the charge of Miss Irma A. Uhde, a senior student in general science in the University of Iowa, who was recommended by Professor Thomas H. Macbride. Miss Uhde conducted the work with fine insight and untiring patience, securing a notably large number of successful infections. Some of the sowings, particularly those of the cedar rusts were made and the records kept by Dr. F. D. Kern. All the work was done under the auspices of the Indiana Experiment Station, and financed from the Adams fund.

Cultures of Uredineæ in 1899

J. C. ARTHUR. WITH the exception of the very important results achieved by Thaxter in the study of American Gymnosporangia, together with similar work by Farlow, Halsted, Stewart, and Carver, only a few attempts have been made in America to trace the connection experimentally between the forms of the Uredinea. The three stages of the clover rust (Uromyces Trifolii) were shown by Howell to be genetically connected and the two forms of the raspberry rust (Gymnocomia interstitialis) by Clinton. A slight amount of work in this line of research, chiefly of a confirmatory character, was carried out between I889 and i898 by Bolley, Stuart, and the writer. The yet unpublished results of Carleton, obtained as part of the work of the division of vegetable physiology and pathology at Washington,2 complete the mention of all American efforts in this line that now occur to the writer. The cultures made during the present season (1899), herein to be described, were conducted, with the exception of a single trial, under glass in the greenhouses of the Experiment Station at Purdue University, and upon plants in pots, the plants remaining under cover until the observations were completed. Material bearing teleutospores of a number of species was collected during the previous autumn and winter and preserved until needed by tying in loose muslin and placing on the ground out of doors. The method generally adopted to secure infection was the same, whether aecidia, uredo, or teleutospores were in hand. The potted plant was first wet with an atomizer, parts covered with a bloom being rubbed with the fingers until the water I Read before the Botanical Section of the Am. Assoc. Adv. Sci., Columbus meeting, August, i899.

Another Fern Rust of the Genus Desmella

The rusts occurring on the ferns are especially interesting due to the ancestry of the hosts and a seemingly corresponding ancestry of the accompanying rusts. The genus Desmella, founded by Sydow on Uredo Aneimiae P. Henn., is particularly noteworthy, as it represents a very primitive form of the Pucciniaceae. Four species were recognized by Sydow (Ann. Myc. 16: 241. 1918) at the time of establishing the genus, and one other tentatively, but the writer considers

Nineteen Years of Culture Work

A series of culture experiments with the Uredinales was begun by the writer in I899, and continued under the auspices of the Indiana Agricultural Experiment Station without interruption until I917, making nineteen consecutive years in which this method of research was consistently pursued. The results of the work were embodied in fifteen reports, printed in the Botanical Gazette, Journal of Mycology, and Mycologia. It is now proposed very briefly to review the work, in order to set forth some of the objects accomplished, and especially to point out the more important of the changing conceptions of the problems forming the ground plan on which the work was projected. The cultures were not undertaken as part of a distinct thesis or circumscribed problem. They were rather the aids in a general taxonomic study of American rusts, which was directed toward supplying a technical description as complete as possible for every species of Uredinales in North America recorded in literature or known to the writer. This ambitious undertaking was definitely begun sometime in the nineties at the invitation of the editors of the North American Flora.

Cultures of Uredineae in 1915

The following is a complete list of the successful cultures made during the year 1915. It is divided into two series, species that have previously been grown in cultures and reported by the writer ...