Nov. 15. 1920 Crownwart of Alfalfa Caused by Urophlyctis alfalfae 299 



all galls as they occur naturally in the field result from the infection of 

 buds in early stages of development as they emerge from the crown of 

 the plant. It is well known that there is an almost continuous succes- 

 sion in the development of buds from the so-called alfalfa crown during 

 the entire year. A portion of those buds which will produce the shoots 

 furnishing the first crop in the spring have begun development as early 

 as the preceding autumn. Generally speaking, the first buds to be formed 

 in the seasonal succession have a point of origin deeper in the soil than 

 those which are formed later, so that many of the buds from which the 

 shoots of the third cutting arise develop from positions quite above the 

 surface of the soil. Buds produced below the soil level in cool weather 

 appear to have a meager protection of scaly covering, and it is for the 

 most part such buds that become infected and give rise to galls. Thus, 

 galls are swollen and distorted bud elements, scales, leaves, and stipules. 



Unless overwintered galls which are described later are discoverable, 

 the disease is first evidenced in the spring by a slight thickening and round- 

 ing of the young buds. During two years this has been observed near 

 Chico, Calif., in the latter part of March or early in April. The diseased 

 buds become more and more rounded as growth progresses and are glis- 

 tening white in color (PI. 54, A). Then, as the infected structures begin 

 to push apart, some of them grow much more rapidly than others until 

 the structure as a whole assumes a conspicuously irregular form. In 

 most cases, however, an examination of the gall will show that it is made 

 up of thick, scalelike layers about a central growing axis (PI. 36, B). 

 Sometimes this axis continues growth in spite of the demands of the mass 

 of developing gall tissue and produces a weak shoot. The earlier and 

 more vigorous buds produce the larger galls. Smaller galls often appear 

 to be developed from smaller buds along the stems below ground that 

 would ordinarily remain dormant. The origin of galls that appear on 

 stems several inches above the surface of the ground in wet weather 

 appears to be due in part to the infection of axillary buds that would 

 never develop in the ordinary course of events and in part to the elon- 

 gation of the stems and petioles which force infected tissue upward. 



Since a large part of the infected buds are developed at a depth of 

 2 or 3 inches below the surface of the soil, the majority of the galls are 

 so far below ground that they escape observation unless the soil is 

 removed from around the plant. If they are of large size some of them 

 come to the surface, where they take on a green color and in extreme 

 cases form a crust of diseased tissue around the base of the healthy 

 stems. 



Another type of gall that is not common results from local infections 

 on young leaves. Such infections give rise to small blister-like galls 

 much like those produced on Sanicula spp. by another species of this 

 fungus which will be mentioned later. 



