DISEASES OF PLANTS. 651 



primary tumor occurs on a stem and the secondary tumor on the leaves, the 

 leaf traces and the loose cellular structure of the petioles are replaced by a 

 firm greenish pseudopith or tumor tissue surrounded by a cylinder of wood, 

 beyond which is a cambium and then a bark covered with cork. 



Full details will appear in a later bulletin. 



The rusts of grains in the United States, E. M. Freeman and E. C. 

 Johnson (C/. 8. Dept. Agr., Bur. Plant Indus. BuT. 216, pp. 87, pi. 1, dgms. 2). — 

 This paper contains the results of recent investigations by the Office of Grain 

 Investigations in cooperation with the Minnesota Agricultural Experiment Sta- 

 tion in regard to the distribution, relationship, physiology, and life histories of 

 the important grain rusts, and gives much new information on the biological 

 forms of rust, vitality of successive uredo generations, wintering of the uredo 

 generations, and climatology in relation to rust epidemics. Former experi- 

 ments on rust are summarized and methods of selection and breeding of grains 

 for rust resistance indicated. 



The rusts discussed in this paper are as follows: Stem rust of wheat {Puc- 

 cinia grmninis tritici), leaf rust of wheat (P. rubigo-vera tritici), stem rust of 

 oats (P. graminis avenw), crown rust of oats (P. coronata), stem rust of bar- 

 ley {P. graminis hordei), leaf rust of barley {P. simplex), stem rust of rye 

 {P. graminis secalis), and leaf rust of rye (P. rubigo-vera secalis). 



As a result of these investigations it is claimed that the morphological char- 

 acteristics, life histories, and physiological specializations of parasitic fungi, 

 including the rusts, may vary with the geographical distribution. The stem 

 rusts of wheat, rye, oats, and barley, both in Europe and America, may produce 

 the secidial stage on the barberry, but that this is necessary for continuous prop- 

 ngation from one season to the next has been disproved by experiments. 



The {Bcidial stage of the crown rusts of oats occurs in Europe on Bhamnus 

 frangula and R. cathartica, and in the United States on R. lanceolata, R. carolin- 

 iana, and R. cathartica. The secidial stage of the leaf rust of rye occurs In 

 Europe on Anchusa officinalis and Lycopsis arvensis. The European and 

 American forms are believed to be identical. The secidial stage of the leaf rust 

 of barley is not known in Europe or America. This rust seems not to have been 

 previously reported in this country. 



The authors report the transferrence in the uredospore stage of the following 

 rusts: "Stem rust of wheat (P. graminis tritici) from wheat to wheat, rye, 

 and barley, but not to oats; from wheat to barley and then to wheat and rye; 

 and from wheat to barley successively three times and then to oats. Stem 

 rust of barley {P. granmiis hordei) from barley to barley, oats, rye, and wheat; 

 from barley to wheat and then to barley, wheat, oats, and rye; and from 

 barley to rye, to barley, and then to wheat, oats, and rye. Stem rust of rye 

 (P. graminis secalis) from rye to rye and barley from rye to barley and then to 

 barley, oats, and rye; and from rye successively to barley, to barley, and to 

 rye. Stem rust of oats (P. gramipis avenw) from oats to oats and barley, but 

 not to wheat or rye. Leaf rust of wheat (P. rubigo-vera tritici) from wheat 

 to wheat, rye, and barley. Leaf rust of barley (P. simplex) from barley to 

 barley only. Leaf rust of rye (P. rubigo-vera secalis) from rye to rye only. 

 Leaf rust of oats (P. coronata) from oats to oats and barley, but not to wheat 

 or rye." 



The following points as to the biologic forms of cereal rusts are emphasized : 

 "(1) The stem rusts on wheat, barley, rye, and oats are undoubtedly biologic 

 forms of the same species, Puccinia graminis; (2) these forms are not entirely 

 confined to their hosts, but vary in range in part according to the host plants 

 they have been recently inhabiting; (3) the leaf rusts on wheat and rye are 

 more highly specialized than the corresponding stem rusts; (4) the stem rust 



