IOWA ACADEMY OF SCIENCES 
and shorter tnaii the normal, j'ellcwish in color, because of the absence 
or clorophyll and much swollen. Usually all of the terminal leaves are 
affected. In such cases the mycelium did not reach the shoot. JL*-.e mycel- 
ium of the fungus stimulates the tissue of the cortex so that swellings 
of the bark and wood occur at the point of infection. The growth of the 
buds causes the formation of the so-called “witches’ broom”. The cortex 
of the “witches’ brooms” is thicker and softer than normal. On the 
upper surface of the leaves of affected branches small yellowish sperma- 
gonia occur between the cuticle and the epidermal cell-wall The yellow- 
ish leaves bear two rows of cups or aecidia, 5-6 on each side on the lower 
surface of the leaf, they are sometimes hemispherical but more frequently 
elongated and elliptical. The lining of the cup is white, but the spores 
are bright orange color. 
The fungus makes its appearance about the middle of July being fully 
mature by the first of August. It is perennial and hence recurs every 
year. 
Microscopical Characters. The small yellow spermagonia on the 
upper surface of the leaf vegetate between the cuticle and the remainder 
of the cell-wall and contain numerous small colorless spermatia. Their 
function is unknown. The leaf is permeated by colorless mycelium which 
sends haustoria into the cells. 
The spores are borne in chains arising from short cells; they vary in 
shape from spherical to polygonal or elliptical; 13-18" x 18 to 22". 
After the spores are discharged the leaves become dry and fall off, 
leaving a large somewhat depressed roundish scar. 
Anatomical Changes in Diseased Tissue. A study of the anatomical 
characters of the diseased structures .has been made by Hartmann^ and 
Anderson”. Hartmann found that in affected branches the peridermlum 
is thicker than normal while the hypodermal collenchyma is not thick- 
ened; resin canals are of unequal size, widely scattered and more abund- 
ant than in healthy tissues; cortical parenchyma more abundant; bast 
fibers not so numerous; xylem and phloem of the fibro-vascular bundle 
not so strongly developed in the diseased; on medullary ray cell more 
compact and the cell walls thickened. Anderson finds fewer stomata in 
diseased tissues, and that the hypodermal strengthening cells are often 
found in nests and groups, the diseased buds being covered over with a 
greater number of scales which are smaller than normal, Resin vesicles 
begin to form even in the first and second year of the diseased shoots, 
increasing in size until in five year old branches the blisters are from 
3-8 mm. in diameter. In normal five year old branches they are never 
more than 1 mm. in diameter. The resin canals of diseased wood are 
usually found in the spring growth. 
Host Plants. Saccardo^ records the following host plants: Picea 
excelsa, AMes alba, A. balsamea, A. pectinata. In Germany it has been 
observed on Albies pectinata, A. nordmanniana, A. cephalonica, A. 
1. Anatomische Yergleicliung der Hexenbesen der Weisstanne mit dem nor- 
malen sprossen derselben. Inaug. Diss. Univ. Frib. 1892. See Tubeuf. L.^c. 
420. 
2. Comparative anatcmy of the Normal and diseased organs of Abies bal- 
samea affected with Aecidium elatinum. 
Bot. Gazette. 24 : 309. PI. U-IS. 
3. Syll. Fung. 7: 823. 
