312 Journal of Agricultural Research voi.xx, No. 4 



not confirmed Magnus' assumption of sexuality in these forms; and from 

 the present account it is obvious that in the formation of the resting 

 spores of U. alfalfae there is no indication of any process of conjugation. 



In order to determine more nearly in what measure the development 

 and morphology of the alfalfa parasite might be common to related 

 forms, the writers examined herbarium material of various species of 

 Urophlyctis, Physoderma, and Cladochytrium. Fresh living material of 

 a species other than U. alfalfae was obtained only from U. pluriannulatus 

 (B. and C.) Farlow (7), occurring in the Pacific States on Sanicula men- 

 ziesii, on which host it was collected in excellent condition near Philo- 

 math, Oreg., on April 7 and May 16, 191 9. As its range extends over 

 the region in which crownwart is known, suspicion has arisen now and 

 then that the two parasites might be identical. This suspicion may 

 now be definitely dismissed. 



Urophlyctis pluriannulatus may very easily be dissected from the 

 cavities in the wartlike protuberances on the stems and leaves of dis- 

 eased plants of Sanicula menziesii (PI. 53). Mounts of thalli consisting of 

 hundreds of turbinate cells and resting spores in a good state of preserva- 

 tion were obtained in this way. Plate 52, A, C, shows two small portions 

 of such a thallus. The general method of development corresponds 

 exactly to that described for U. alfalfae, yet morphological differences 

 sufficient to separate the two as distinct species are readily recognizable. 

 Greater dimensions are characteristic of U. pluriannulatus, both of 

 turbinate cells (which measure approximately 22 /x in length and 18 /x 

 in major diameter, against 19 /x length and 15 /x major diameter for 

 U. alfalfae), and of resting spores, the equatorial diameter here ranging 

 from 45 to 60 /x, as contrasted with 40 to 50 xx for U. alfalfae. The 

 turbinate cells of U. alfalfae produce usually a maximum of four to five 

 secondary turbinate cells, a greater number being occasionally produced, 

 however, by the very large primary turbinate structures; whereas in 

 U. pluriannulatus, turbinate cells not infrequently produce seven or eight 

 turbinate cells of the next order, five or six being the rule. An interesting 

 but rather inconspicuous difference in the structure of the rhizoids on the 

 resting spores may be noted. Since the primary branches are inserted 

 at nearly right angles in U. alfalfae while the corresponding angles tend 

 to be much smaller in U. pluriannulatus, there is brought about a differ- 

 ence that might crudely be compared, for example, to the difference in 

 habit between a palm and an elm. In U. pluriannulatus, too, the haus- 

 toria are inserted slightly nearer the equator than in the alfalfa parasite. 

 But the most unmistakable specific difference is to be found in the 

 number of haustoria on each resting spore, which in U. alfalfae varies 

 from 9 to 15 and in U. pluriannulatus ranges from 14 to 24. (Compare 

 PI. 48, E, with PI. 52, D.) 



In this connection it may be mentioned that resting spores from herba- 

 rium material of all the other species of Urophlyctis examined, after being 



