R O SE R US TS. 



609 



The operations of another year will include the use in large circular baskets of very slight depth. The gar- 



of seeds successfully ripened within these gardens. dening equipment in use is of the simplest character. 



Among these far yiien may be seen liberal quantities of It includes many large jars, barrels for storing water, 



little beans and seeds of the foo qua. These are dried and different kinds of baskets. 



ROSE RUSTS. 



No FUNGUS is more familiar to the horticul- 

 turist than that which ccmstitutes the orange 

 rust of the blackberry. For this reason I 

 wish to refer to it in order to call attention to 

 a certain rust of roses. The latter resembles the former 

 in color, and both are of a deeper orange color and 

 larger in mass than is common in fungi of this class. 

 This rose fungus differs, however, in several points. 

 It grows not only on the blades of the leaves, but on 

 the stems, petioles and midribs. It forms not an 

 expanded layer, but a strongly convex pustule, often of 

 considerable size, and the stem or leaf is frequently 

 bent away at that point. It occurs at the same time of 

 year as the orange rust, or a little later. Microscopic- 

 ally, it resembles the orange rust in having the spores 

 in chains, and in this respect both are like the cluster- 

 cup of the barberry, which is the ascidial form of wheat 

 rust. The cluster-cup spores, however, are included in 

 a sort of cup or peridium, which is wanting in both the 

 others. Still, it may be that each is the aecidial stage of 

 some fungus. No other fungus form has ever been cer- 

 tainly found to be associated with the orange rust. 

 With the rose rust, however, two other forms have 

 been found associated, corresponding to the red and 

 black rust of wheat. The three forms may be found on 



the same rose bush, 

 at the same time, inti- 

 mately associated. 

 The uredo spores are 

 delicate orange or yel- 

 low spores, consisting 

 of a fi n e 1 y warty 

 membrane, inclosing 

 i n spherical form its 

 protoplasm and 

 orange coloring mat- 

 ter. Each i s borne 

 on a short pedicel, 

 from which it easily 

 falls when ripe. 

 These spores break 

 through the epidermis 

 of the under leaf sur- 

 face in small pustules, 

 the pustules being sur- 

 rounded by a row of 

 curved sterile bodies 

 much larger than the 

 spores. Later, but while both kinds of orange spores 

 are still fresh, black spores begin to appear, commonly in 

 the same clusters with the uredo spores. They are rather 

 tall spores, and stand at the top of stalks somewhat 



Fig. 2. Spores of Rose Rust. 



Fig. 3. Spores 

 OF Rose Rust. 



longer than themselves, so that they are easily seen with 

 the aid of a magnifying glass. In wheat rust the black 

 spores have only two cells ; in rusts of this genus 

 (phragmidium) there are several, or many cells. This 

 species commonly has about six cells, the number vary- 

 ing from three to nine. On account of its pointed apex, 

 it is called Pliraginidiiiin mitcronatiim 

 (Fig. 3). Other equally pointed or 

 mucronate species were not known when 

 this was named. 



This fungus, in all its forms, is com- 

 mon on both wild and cultivated roses. 

 The first stage has been observed as 

 early as April, and the last as late as 

 November. The form shown in Fig. i 

 is not so common, but still is not rare. 

 It is not known to have but one stage, 

 and this occurs on the stems, or some- 

 times on the petioles, forming compara- 

 tively large black masses, i. t'., per- 

 haps sometimes an inch long. As a 

 microscopic object, this species is re- 

 markable for the beauty of its spores, 

 which is owing largely to the presence 

 of the very long tlexuous pedicels. It is called Phragmid- 

 ium speciosur/i. 



The third species which grows on roses in America 

 may not be very rare, but if not rare, it has not been dis- 

 tinguished from the first. It is very similar to the first, 

 but differs from it constantly in the larger number of 

 cells in the black spores, which number sometimes as 

 many as thirteen, but commonly about nine to eleven 

 Fig. 2 represents one of the black spores {a) with its swol- 

 len pedicel, two uredo spores (/') and two of the sterile 

 bodies (< ) which accompany the latter. This is apparently 

 the form called by Mr. Peck, in the New York Museum 

 'R.e-poxls, P/iragmiditctn miicronatiim, m^x. Aiiiericaiiuin, but 

 I am convinced from comparison of authentic specimens 

 that it is identical with the European Pliragmidiiim 

 Rosir-alpinu-. All of these species are injurious to rose 

 bushes, but the injury is not very conspicuous, and ap- 

 parently not very serious in its extent. When any of 

 them is troublesome, some relief should be expected 

 from burning the fallen leaves, taking care, if possible, 

 that none escape. Only the black spores are supposed 

 to survive the winter, and these are destroyed by the 

 burning. The effect of the fungus is to make many of 

 the leaves fall prematurely. 



The rose rusts are interesting to the botanist on ac- 

 count of their life history and the remarkable beauty 

 of their spores. 



Harvard University . A. B. Seymour. 



