35 M 



Jan. 1904] Cultures of Uredineae in /poj. IS 



rile that the data are yet too meager to make it worth while to 

 undertake to decide upon the nomenclature of the forms or 

 species, which ever they may be called. 



In addition to the foregoing- results seven species of rusts 

 were grown, establishing aecidial and teleutosporic connections, 

 not heretofore recorded. The species are partly autoecious and 

 partly heteroecious rusts. 



i. Mel am PSORA Medusae Thtim. Teleutosporic material 

 on Populus del t oides Marsh, was obtained in the vicinity of La- 

 fayette, hid., and although of inferior quality, for the poplar 

 rust was not abundant in this region last year, it was sown on 

 Larix deeidua Mill. (L. Iluropaea DC.) April 28. After a 

 rather long interval of 16 days I was surprised and gratified 

 to observe the beginning of spermogonia (May 14) in good 

 quantity; and five days later (May 19), the aecidia appeared, 

 and proved to be a caeoma-form. A sowing on this host was 

 tried last year" without infection, which is, however, easily ac- 

 counted for by the fact that the host plants employed in 1902 

 were very feeble. For the supply of Larix, used this year I am 

 indebted to the generosity of R. Douglas' Sons, proprietors of the 

 Waukegan Nurseries at Waukegan, 111. They sent without re- 

 muneration 25 very thrifty young larch, suitable for 6-inch pots, 

 which made vigorous growth when brought into the green- 

 house. 



This species is the American representative of the European 

 M. populina Lev., both species having their aecidia on Larix. 

 That the American form is specifically distinct from the Euro- 

 pean was pointed out by Klebahn 12 in 1899, the differences being 

 especially marked in the form, size and markings of the uredo- 

 spores, and in the apical thickening of the teleutospores. The 

 American form may be characterized as follows: 



Mklam psora Medusae Thuem. 



( . Spermogonia epiphyllous. numerous scattered, inconspicuous, pale 

 yellow, papilliform by vertical sections shown to be columnar or hem- 

 nispherical, raised above the surface, 40-55//., in diameter. 



I. Aecidia hypophyllous, numerous, scattered, small, less than .5 mm. 

 in diameter, pale yellow: peridium absent; aecidiospores catenulate, 

 globoid, 20 a in diameter: wall colorless, nearly 3 fJ- thick, finely verru- 



II. Uredospores amphigenous. or sometimes only hypophyllous, 

 roundish, small, less than .5 mm. in diameter, early naked, somewhat pul- 

 verulent, orange yellow ; uredospores oval, or obovate-oblong, 15-18 by 22- 

 80, usually flattened on opposite sides; wall colorless, 2.5-3//, thick, or up 

 to 10// nn the flattened sides, sparsely and evenly echinulate with fine 

 papillae, except on the flattened sides which are smooth; paraphyses 



" Bot. Gaz. 35:11. 1903. 

 "Ztschr. f. Pfl.-Kr. o:144. 1899. 



