22 



FARLOW ON THE GYMNOSPORANGIA 



The spores differ in several respects from those of the species already described. They 

 are usually two-celled, but it is not at all unusual to find three cells, as is shown in Plate 

 2, fig. 25. They are broadly ovate, and attached to pedicels which, instead of being of 

 nearly equal diameter throughout, as in the other species, are very much swollen just 

 below the spores, in fact often more so than is shown in figs. 24 and 25. The breadth of 

 the upper part of the pedicels, however, varies with the state of expansion of the spor- 

 iferous masses, being especially broad when they are young, and slenderer when they are 

 old. The base of the spores where the pedicels are attached is very broad, and when the 

 masses are quickly swollen, especially by means of re-agents, the inner portion of the 

 pedicels expands more rapidly than the outer part, and the latter is ruptured just below 

 the spore, so that there is left a hyaline ring surrounding the pedicel at the base of the 

 spore. 



The growth of the promycelia is peculiar in G. clavipes. As a rule the promycelia of 

 the other species are given off from the cells near the part where they are in contact with 

 one another, and they are either single or double, or, as is very frequently the case, four 

 are given off at diametrically opposite points. Occasionally one sees a promycelium form- 

 ing at the apex of the spore, and such a case, occurring in G. macropus, is shown in PI. 1, 

 fig. 6. In G. clavipes it is very common for promycelia to be formed at the apex as 

 shown in PI. II, fig. 27, and another promycelium near the septum. The most peculiar 

 form is that shown in fig. 26, where the spore has fallen from its pedicel, and a 

 promycelium is produced both at the apex and the base. This form I have not found to 

 be common, but it can be seen without difficulty. 



The present species, in spite of some striking peculiarities, presents a general resem- 

 blance to G. conicum, which is common enough in Northern Europe, but is rare in this 

 country, if indeed it occurs at all. G. clavipes was first separated from G. conicum in 

 consequence of the swollen pedicels and the formation of promycelia at the apex ob- 

 served by Peck. Curtis, judging from the specimens in his herbarium, did not distin- 

 guish G. clavipes from Podisoma Juniperi Lk. which is the same as the G. fuscum of the 

 present article, for the specimen of Michener No. 4830, from Pennsylvania, and a speci- 

 men collected by Curtis himself at Hillsboro, N. C, certainly belong to G. clavipes. A 

 second specimen from Society Hill, S. C, marked simply Gymnosporangium, also belongs 

 to the present species. The question whether G. clavipes is merely a form of G. con- 

 icum or not, is not easily answered. The general appearance of the sporiferous masses 

 is the same, and if the distortions produced are different, it may be said that that may 

 be accounted for by the fact that in Europe G. conicum grows on J. communis, while 

 what we call G. clavipes grows on J. virginiana. The swollen pedicels, even admitting 

 that the amount of the swelling varies in different specimens, has not been noticed in 

 European specimens of G. conicum, and, although Oersted figures one spore in which 

 the promycelium is given off from the tip in G. conicum, it seems nearly certain that no 

 European species has the apical form of germination, unless exceptionally. Taking these 

 facts collectively, I should think that G. clavipes was a distinct species peculiar to 

 America, and that it was not quite certain that the true G. conicum occurs with us. 

 A few forms which can hardly be included in G. clavipes, I should refer to G. conicum 

 with a doubt. 



