. The British rust fungi (Uredinales), their biology and classification. Uredineae. 58 MELAMPSORA PINITORQUA point, combined with this lateral curvature, causes S-shaped distortions which have given rise to the name " Pine Branch Twist" for the disease (Fig. 35). It is suggested by Massee that the aecidiospores can repro- duce the ascidia and thus propagate the parasite on the Pine without reference to the alternate host, but no proof is given of this statement. The mycelium is almost certainly perennial in the affected branch, and thus fresh outbreaks arise year by year more or less
. The British rust fungi (Uredinales), their biology and classification. Uredineae. 58 MELAMPSORA PINITORQUA point, combined with this lateral curvature, causes S-shaped distortions which have given rise to the name " Pine Branch Twist" for the disease (Fig. 35). It is suggested by Massee that the aecidiospores can repro- duce the ascidia and thus propagate the parasite on the Pine without reference to the alternate host, but no proof is given of this statement. The mycelium is almost certainly perennial in the affected branch, and thus fresh outbreaks arise year by year more or less, according to the weather in the spring. If the aicidiospores are blown on to a leaf of Aspen, they germinate there and the mycelium produces uredospores during. Fig. 35. Melampsora pinitorqua (from a German specimen, ex herb. Sydow). rt, a young shoot of Pine, in June, with newly-formed leaves, showing three Cffiomata («), shaded ; the leaves have been removed from the affected portion, which is beginning to be curved; b, a Cffioma, xlO; c, aecidiospores; d, old leaf of Aspen, showing numerous teleuto-sori on the lower surface; e, teleutospores. the summer: these are usually so abundant as to cover the underside of the leaves, and the parts on which they occur show plainly as yellow spots on the upper side. For a time, the uredospores spread the disease rapidly during the growing season, until sometimes all the leaves of a tree are more or less attacked and are covered with a bright orange powder. As the leaves begin to die, teleuto-sori are formed; at first these are brown, and show as little angular crusts on the under side. Afterwards, when the leaves are fallen off, the crusts begin to turn almost black as the teleutospores mature. These spores are produced beneath the epidermis, standing erect and side by. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illust
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