May 27, 1910] 



SCIENCE 



833 



showed the value of inferences drawn from 

 homology. 



The writer now desires to make one other 

 prediction concerning a possible relationship, 

 and the character of a form yet to be discov- 

 ered, in which both analogy and homology 

 have been employed. 



In his paper on " Cultures of Uredinae " in 

 1908 Dr. J. C. Arthur reports the establish- 

 ment of a relationship between ^cidium 

 Blasdaleanum and Gymnosporangium Liho- 

 cedri. As explained there A. Blasdaleanum 

 is morphologically unlike the other Bmsteliw, 

 having instead, characters like the ordinary 

 secial forms of Puccinia and Uromyces. How- 

 ever, it inhabits hosts belonging to the apple 

 family, the hawthorn and service-berry, and 

 these cultures show that it is undoubtedly 

 genetically connected with a cedar-rust. 

 There is, in the Pacific coast region, another 

 secial form of the same type, on members of 

 the apple family, JEcidium Sorhi on the 

 mountain ash and crab-apple. Although 

 ^cidium Sorhi is of the same general type as 

 A. Blasdaleanum, it has some very pronounced 

 characters which show that it is specifically 

 different. There is in the whole Pacific slope 

 region at present no known Gymnosporangium, 

 except G. Libocedri and it is at once apparent 

 that the telial stage of A. Sorhi is still to be 

 discovered. There is, however, within this 

 range a cedar-rust in the form of Uredo 

 Nootkatensis on Chamcecyparis Noothatensis, 

 the yellow cedar, from Alaska. That Uredo 

 Noothatensis is the uredinial stage of a 

 Gymnosporangium, which has in its life-cycle 

 an fecial stage on hosts belonging to the apple 

 family, has been previously suggested.* The 

 basis for such an argument has been fur- 

 nished by the elucidating researches of Dr. 

 Arthur of which his new classification' of the 

 TJredinales is the result. Prom this work it 

 appears justifiable to assume that the pro- 



*Bull. Torrey Botan. Club, 35: 601-502, 1908. 



^ " Eine auf die Structur und Entwieklungg- 

 geschichte begrundete Klassifikation der Uredi- 

 neen," Result. Set. Congr. Bat. Vienne, 331-348, 

 1906, and " Reasons for Desiring a better Classifi- 

 cation of the Uredinales," Jour. Myc, 12: 149- 

 154, 1906. 



duction of all four spore-forms, pycnia, aacia, 

 uredinia and telia, was doubtless the early 

 condition in evolution, and that the suppres- 

 sion of one or more of these forms is a result 

 of later influences. In most of the groups or 

 tribes this four-spored condition not only still 

 persists but usually the larger number of 

 species belong in that class. Arguing from 

 this point of view Dr. Arthur has predicted 

 that sooner or later a Gymnosporangium 

 ought to be discovered which would possess 

 uredinia, i. e., have all four spore-forms. 

 Since the uredinial stage is unknown in any 

 of the true Gymnosporangium-Rwstelia com- 

 binations it seems probable that if it exists 

 at all it is likely to be in a species which has 

 an secial form like that of the species of Puc- 

 cinia which ordinarily possess uredinia. With 

 the above ideas as a basis the writer suggests 

 the possibility of a relationship between the 

 cedar-rust, Uredo Nootkatensis and Mcidium 

 Sorhi on the mountain ash and crab-apple. 

 Baranoff Island, Alaska, is the type locality 

 of the Uredo; ZUcidium Sorhi has also been 

 collected on the same island, an item from 

 geographical distribution which lends further 

 support to the supposition. Arguing from a 

 comparison with G. Libocedri, the only cedar- 

 rust known to have the puccinia-type of secia, 

 the new telial stage should be foliicolous and 

 have spores two or three times septate. If 

 the above contention is true it may well be 

 asked why G. Lihocedri should not have a 

 uredinial stage if there is anything in anal- 

 ogy. The answer is that it probably does but 

 that it is unknown because no well-directed 

 attempt has yet been made to collect it. 



Prank D. Kern 



PUEDUE UlfrVEBSITT, 



Lafayette, Ikd. 



the miocene horizons at porters landing, 

 Georgia' 



The following section of the exposure at 

 Porters Landing is adapted from the descrip- 

 tion of it given by Mr. Earle Sloan in his 

 " Catalogue of the Mineral Localities of South 

 Carolina," page 273. 



' Published by permission of the Director of the 

 United States Geological Survey. 



