RicE: INTERNAL SORI OF PUCCINIA SORGHI 39 
1917/Colley, R.. |Cronartium ribicola| III |Ribes sp. In pith and peri- 
HZ) cycle of petioles. 
1917|\Colley, R. |Cronartium ribicola| 11 |Ribes hirtel- \In cortex of stems. 
H. (8) lum Michx. 
1917|\Colley, R. |Cronartium ribicola I |Pinus In resin ducts of 
H. (8) Strobus em. 
1920 20lTay! Puccinia albiperidia| Ribes gland- \In fruit and seeds. 
Minnie (22); Arthur ulosum 
eee Puccinia graminis- II |Triticum sp.|In pericarp of hilar 
ford, C. W.|  tratict Ill 
(11) 
1923/Dodge, B. |Pucciniasirum Rubus strigo-|In cortex of stem. 
8a americanum II |sus 
(Farl.) 
Such a list of cases of internal sori indicates that they are 
by no means rare. They are of interest in connection with the 
whole problem of the interrelations of host and parasite, as well 
as in connection with the problem of the causes underlying the 
production of the different spore forms of the rusts. In a number 
of cases mentioned above the occurrences were reported by the 
authors as having a possible bearing upon the overwintering of 
the rust (Smith, 19, 20; Eriksson & Henning, 9; Bolely, 4; Prit- 
chard, 4, 15, 16; Beauverie, 2; Hungerford, 11). Others report 
merely brief notices of an abnormality (Klebahn, 12; Marryat, 
12a; Clinton, 5; Stamfli, 21; Reynolds, 17; Atkinson, 23; Edger- 
ton, 23; Reddick 23; Fromme, 10; Taylor, 22; Dodge, 8a). Wolf 
(23), Adams (1), and Colley (7, 8) have given more attention to 
the cases. They agree in considering internal spore-formation as 
a non-adaptive, abnormal development of the parasite. Wol 
(23) lays to chance the more deep-seated position of some sori, 
which causes them to push inward and open toward the center 
as the line of less resistance. He believes the causes must be the 
same as those which bring about production of spores in general. 
Adams (1) considers the development of the internal uredosori 
favored by an abundant mycelium and by the texture of the 
Dianthus leaf, which ‘‘allows wide ramifications of the rust 
