A text-book of mycology and plant pathology . H. S., and Crabill,C. H., Techn. Bull. 9, Va. Agric. Exper. Stat., May, 191S) midium from neighboring genera. The teliospores are two- to several-celled by transverse septa. An important species is the Rust of Roses,Phragmidium subcorlicium, which has a spindle-shaped teliospore withsix to eight cells. Gymnosporangium is a genus of heteroecious rusts the aecia of whichoccur on Rosacea (except one on Hydrangeac^ and one on Myri- RUST FUNGI 209 CACE^) while the three-, four or five-celled teliospores are foundon CupRESSiNE^ (ChaftKecyparis, Cuprcssus
A text-book of mycology and plant pathology . H. S., and Crabill,C. H., Techn. Bull. 9, Va. Agric. Exper. Stat., May, 191S) midium from neighboring genera. The teliospores are two- to several-celled by transverse septa. An important species is the Rust of Roses,Phragmidium subcorlicium, which has a spindle-shaped teliospore withsix to eight cells. Gymnosporangium is a genus of heteroecious rusts the aecia of whichoccur on Rosacea (except one on Hydrangeac^ and one on Myri- RUST FUNGI 209 CACE^) while the three-, four or five-celled teliospores are foundon CupRESSiNE^ (ChaftKecyparis, Cuprcssus, Junipcnis, IJbocedrus).One autoecious species is G. bermudianum which produces both itsaecia and telia on junipers (/. bermudianum). Kern gives thirty-twospecies as the number for North America and in vol. 7, North AmericanFlora, part 3, pages 188-190, gives a useful key for the identificationof the species. Gymnosporangium botryapitcs causes fusiform swellings on the whitecedar, ChamcBcyparis thyoides, on which swellings the two- to four-. FiG. 79.—Cedar rust on apple, roestelia stage with pustules. (After Jones andBartholomew, Bull. 257, Agric. Exper. Stat., Univ. Wise, July, 1915.) celled teliospores are formed. The aecia occur on two species of shadbush: Amelanchier canadensis and .4. intermedia (Fig. 73). In Gymnos porangium nidus-avis, the telia arise from a perennialmycelium which often dwarfs the young shoots and causes birds-nestdistortions in which usually there is a reversion of the leaves to thejuvenile form, sometimes causing gradual enlargements in isolatedareas on the larger branches of Juniperus virginiana with aecia onseveral species of Amelanchier (Fig. 73). Juniperus communis is the host of the telial stage of G. clavaricEforme,which appears on long fusiform swellings of various-sized branches,14 2IO MYCOLOGY scattered, or aggregated and its aecia on seven species of Amelanchier,one each of A ronia and Cydonia. Gymnosporangium Ellisii (Figs. 74 and 75) in
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