224 MANUAL OF POISONOUS PLANTS 



plants. Clements arranges the rusts with the Ascomycetes. He considers that 

 the apothecium is reduced.** 



Puccinia, Pers. Rust 



Teleutosori flat, usually powdery masses; teleutospores separate with pedi- 

 cels, usually consisting of 2 cells, occasionally 1 -celled, or sometimes more than 

 2 cells; the germ pore of the upper cell, at the apex, the lower cell with the 

 germ pore placed laterally below the septum; the promycelium septate with 

 several sporidia. The teleutospores germinate immediately in some species, in 

 others after a period of rest. About 700 species. 



Puccinia graminis, Pers. Common Grass Rust 



The aecidiospores generally circular, thick swollen with reddish spots sur- 

 rounding the infected area, yellow below; peridia cylindrical with whitish torn 

 edges; spores subglobose smooth orange yellow, 15-25 ^ in diameter; spermo- 

 gonia on the upper surface consisting of small black dots, uredosori orange red, 

 linear but often confluent, forming long lines, powdery masses; spore elliptical, 

 ovate or pyriform, echinulate, orange yellow 25-38 x 15-20 m; germ pores 2 

 above the center on each side; teleutosori persistent; open, generally forming 

 lines on the sheaths, stems and inflorescence; teleutospores .fusiform clavate 

 constricted in the middle generally smaller below the apex, thickened, rounded 

 or pointed smooth chestnut brown 15-20x35-65 /i; pedicels long and persistent. 



The life history of common grass rust is as follows : The common rust pro- 

 duces three stages. One stage occurs in the barberry and is known as the 

 cluster cup fungus. This stage makes its appearance in the northwest some 

 time during the month of June, in the latitude of Ames, a little before the 

 middle of the month. An examination of an affected leaf will show small black 

 specks on the upper surface, surrounded by a yellow spot; this is known as the 



* The Genera of Fungi. 5. 98. 



*• Christman in his studies (Bot. Gaz. 39:267; Trans. Wis. Acad. Sci. 15:517; Bot 

 Gaz. 44:18.) of the common rose rust (Phragmidium speciosum) finds that the ends of 

 the hyphae produce a terminal sterile cell and a lower fertile one; the fertile cells fuse in 

 pairs with one another, the cell walls breaking down. The nuclei lie side by side and 

 divide, two of the daughter nuclei remaining in the lower part and two passing to the 

 upper part of the dividing cell. Then the upper portion becomes separated by a^ trans- 

 verse wall and becomes the first spore mother cell. These fusing cells are approximately 

 equal. Blackman (Ann. Bot. 18:323, See also Ann. Bot. 20:35.) in his studies of 

 another species of the same genus, states that the fertile or female cell contains a larger 

 nucleus and that the male cell is reduced; that the hyphae which gave rise to an aecidium 

 first cut off a sterile cell, and the cell below which at first only contains a single nucleus 

 becomes binucleated because of the passage of the nucleus from an adjoining cell. Suc- 

 cessive divisions of the nuclei occur and finally we have a chain of spore mother cells; 

 each having a pair of nuclei. 



Dr. Olive (Annals of Bot. 22:331. Bull S. Dak. Agrl. Ex. 81:119) who has made 

 a close careful study of Triphragmium ulmariae comes to the conclusion that two fusing 

 gamets as well as their nuclei are approximately equal, and that the two garnets differ 

 somewhat in time of development. "That the apparently normal and regular occurence 

 at the base of certain young aecidia of one to many multinucleated cells, points to the 

 necessity of a broader conception as to the mode of development of the aecidium-cup than 

 that held by either Blackman or Christman. While the part which these multinucleated 

 cells take in the development of the aecidium is as yet somewhat obscure, the evidence 

 appears to point to the conclusion that they are sporophytic structures and that they result 

 from the stimulated growth which followed sexual cell fusions. Should this prove true, 

 it is obvious that the 'fusion cell' does not at once function as a 'basal cell*, at the bot- 

 tom of each spore-row, as maintained by Christman for this type of Rust. Further, the 

 occurrence of occasional instances suggesting 'nuclear migrations,* undoubtedly of a path- 

 ological nature, between the multinucleated cells of Puccinia Cirsii-lanceolati, throws doubt 

 on the idea as to the normal origin of the binucleated condition in the aecidium-cup by 

 this means." 



It may be of interest further to state that Holden and Harper (Trans. Wis. Acad. 

 Sci. 14:63.) have studied a species of Coleosporium and find that the fusion nucleus divides 

 in a manner similar to that of higher plants. 



