DUGGAR. — UKEDO POLYPODII. 397 



genera are sufficient to separate them. He would therefore refer the 

 form on Phegopteris Dryopteris to Uredo Aspidiotus Pk.,* which is 

 distinguished by having the sori on both sides of the leaf, but more 

 abundant on the upper side ; the spores are moi'e or less polygonal or 

 oval, measuring 36-56 X 27-40 /i, with from six to eight germ pores 

 iri'egularly distributed over the surface. Dietel also emphasizes the 

 constant appearance of thin-walled and thick-walled spores in both 

 Uredo Aspidiotus Pk. and U. Polypodii (Pers.) DC. He mentions 

 finding intermediate stages between the thin and the thick-walled 

 spores, which seem to show that the one is developed from the other ; 

 but he entertains doubts as to which might be the primary form. 

 Bearing in mind the suggestion of Winter as to the possibility of a 

 teleutosporic form, he made cultures of the thick- walled type, yet the 

 germination was that of true uredospores. It was then concluded that 

 there were two kinds of uredospores in each of these species. It was 

 also found that the thin-walled spores possess the constant character of 

 four germ pores equatorially arranged, but this will be discussed later. 

 As far as I can ascertain, no views have been advanced as to the 

 definite relationship of the thick-walled and thin-walled spores in re- 

 gard to the relative time of development. For this purpose, as well 

 as for a careful interj)retation of specific distinctions, fresh specimens 

 are essential. For the present study I was fortunate to secure from 

 Arlington, Mass., fresh material of Uredo Polypodii (Pers.) DC. on 

 Cystopteris fragilis ; and at Shelburne, N. H., I found a supply of the 

 form on Phegopteris Dryopteris described as Uredo Aspidiotus Pk. 

 Access to an abundance of herbarium material, to be mentioned later, 

 left no doubt as to the correct identification of the above named speci- 

 mens. These two forms were carefully examined and compared in the 

 fresh condition. In the form on Cystopteris fragilis the sori appear 

 only on the under side of the leaf, and the spores are often smaller 

 than in the case of the form on Phegopteris Dryopteris, but with 

 these exceptions the general characters are the same. In either case, 

 sections across the youngest sori show the thin-walled spores attached, 

 and no thick-walled spores are present. The thin-walled spores are 

 irregularly ellipticaP or oval (Figures 1, 2, 5, and 6), with very 

 little trace of the orange contents. The whole number of germ pores 

 is difficult to ascertain. In optical section one germ pore is often 

 visible on each side about half-way between the apex and base, but 

 more than one germ pore to a side is not infrequent, even in those 



* Twenty-fourth Report of N. Y. State Museum, p. 88. 



