376 



THE FUNGI WHICH CAUSE PLANT DISEASE 



P. cerasi Ces. is a hemi-type on cherries in Southern Europe. 



P. ribis-caricis Kleb. 



I on Ribes. II and III on Carex. 



Klebahn -^* differentiates five species of Puccinia on Ribes be- 

 longing to the Ribis-Carex group. These are P. pringsheimiana 

 (I.=^E. grossulariffi.) P. ribis-pseudocyperi, P. ribis nigri-acutje, 

 P. ribis nigri-paniculatiE and P. magnusii. 



P. asparagi D. C.^^s-^w 



I. Peridia in elongated^ patches upon the stems and larger 

 branches, short, edges erect, toothed. Spores orange-yellow, 

 round, very finely echinulate, 15-26 ju in 

 diameter. 



II. Uredinia brown, flat, small, long 

 covered by the epidermis. Spores irregu- 

 larly round or oval, clear-broviTi, echinu- 

 late. 18-25 X 20-30 M- 



III. Telia black-brown, compact, pul- 

 vinate, elongate or roimded, scattered. 

 Spores oblong or clavate, base rounded, 

 apex thickened, darker, central con- 

 striction slight or absent, deep chest- 

 nut-brown, 35-50 X 15-25 m- Pedicels 

 persistent, colorless or brownish, as long 

 as or longer than the spores. 



An autoecious eu-type on Asparagus, 

 cultivated and wild. The fungus has 

 been known in Europe since 1805 but did not attract attention 

 in the United States until 1896 in New Jersey ^^^ when it began 

 its devastating westward migration ^^^ across the country reaching 

 California in 1900 or 1901. 



The aecial stage appears in early spring; the seciospores may 

 germinate at once or if dry remain viable for several weeks, 

 their germ tubes penetrating the host in most cases stomatally. 

 The uredinia appear in early summer soon after or with the aecial 

 stage and, wind borne, distribute the fungus. The uredinio- 

 spores remain viable a few months when dry. The telial stage 

 appears late in the season and germinates only after hibernation. 



Unicellular spores, mesospores, are sometimes met. 



Fig. 272. — Section through 

 black nist pustule, show- 

 ing teliospores of P. as- 

 paragi. After Smith. 



