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IOWA ACADEMY OF SCIENCES 
by Mr. Freeman\ but he does not report the fungus on P. granclidentata, 
or P. tremuloides. It is especially common on the species of willow of 
which Salix richardsoni is the type. 
Black Knot of Plum. In concluding the portion of this paper bear- 
ing upon the subject of fungus diseases mention should be made of Ploiv- 
rightia morbosa upon Primus demissa and P. americana. The writer 
observed a few of the wild specimens of. Prunus americana affected by 
fungus in the vicinity of Greeley, and it is common on Prunus demissa 
in the Uintah Mountains, in some places, and doubtless in other sections 
of the Rocky Mountains. It has not been observed in the region under 
consideration, on the cultivated Prunus ojmerieana. 
Root Rot. Mention may also be made here of a root rot that affects 
shade and forest trees, as Acer saccharinum, {A. dasycarpum) and Fraxi- 
nus viridis. The disease is quite common both in the Salt Lake country 
and in the eastern Rocky Mountain region where it is net uncommon to 
find forest and shade and fruit trees assuming a yellow tint. By many 
persons this is supposed to be caused by an excess of alkali in the soil 
and no doubt such is frequently the case but the writer’s attention was 
called by Professor Paddock to the yellowing of fruit, shade and forest 
trees in the vicinity of Fort Collins, which Vv^ere undoubtedly affected by a 
root rot iungus. in one instance, Deniatophora necatrix was found in 
connection with the roots, but there wms not time for a thorough investi- 
gation and Professor Paddock was already carrying on w'ork upon similar 
freest 
Disease Due to Flowering Plants. Throughout the entire Uintah 
Mountains several parasites of the genus Arceuthobium are quite trouble- 
some to conifers. One species A. americanum is common on Pinus mur- 
rayana, another species, A. robustum, also occurs in the Rocky Mountains 
and was abundant in the foothills of the front range west of Fort Collins, 
and A. douglasii is found in Clear creek canon. The genus Arceuthobium 
belong to the order Loranthaceae or mistletoe family, represented in the 
southern states by Phoradendron fiavescens, called the American mistle- 
toe v/hich is abundant on various species of deciduous trees like the oak 
and elm. This mistletoe is very extensively used for Christmas decora- 
tion. Several other species of Plici'adendron are native to the west, one 
only occuring in the Rocky Mountain region, namely, P. juniperinum, 
The only eastern representative of Arceuthobium is A. pusillum which 
produces dwarf or clustered stems on the black spruce, Picea nigra in 
eastern North America, especially in the Adirondacks, in New York, New 
Hampshire and Maine. It has been made the subject of several notes by 
PeclP ^vho gives a description of the parasite on the black spruce Picea 
nigra and by Von SchrenlU who calls attention to the “witches’ brooms” 
produced by it on Picea mariana and the injury done especially in causing 
premature death. 
1. Minn. Bot. Studies. 4 : 428. P. deltoides acc. to Kew Monilifera grandi- 
deni la. i opuliis anguluta — P. monilifera, and both — P. deltoides according to 
Bril ton and Brown. 
2. Professor Paddock has recently discussed this trouble in a short paper. 
Bull. Col. Agrl. Exp. Sta. 69 : 4. 
3. Kept. New York State Museum of Natural History 25 ; 69. 27 : 112. 28 : 83. 
4. Rhodora 2 : 2-5 pi. vb. Zeitsch f. Pflanzenk 11 : 137. 
