. Botany for high schools and colleges. Botany. 314 BOTANY. or less elongated lines. In color they are almost invariably brown or nearly black, in marked contrast to the reddish yellow (orange) uredosporcs. In some cases they are joroduced early in the season, but in the greater number of cases they appear in the autumn, and then remain through the winter upon the dead stems of their host plants. The following spring the teleutospores germinate by sending out a jointed filament {i\\Q promycelmm) fi'om each cell; this grows to several times the length of the teleutospore, and then sends out a f
. Botany for high schools and colleges. Botany. 314 BOTANY. or less elongated lines. In color they are almost invariably brown or nearly black, in marked contrast to the reddish yellow (orange) uredosporcs. In some cases they are joroduced early in the season, but in the greater number of cases they appear in the autumn, and then remain through the winter upon the dead stems of their host plants. The following spring the teleutospores germinate by sending out a jointed filament {i\\Q promycelmm) fi'om each cell; this grows to several times the length of the teleutospore, and then sends out a few lateral branches, each of which bears a small terminal cell, a sporid- ium (Fig. 217, A and B, and Fig. 218). The sporidia are extremely minute, and, as a consequence, are carried about from place to place in the wind with great ease. When they fall upon the joroper plant, each sporidium sends out a minute filament, which perforates the epidermis-cells, and from these passes into the leaf parenchy- ma, where it develops into a mycelium (Fig. 217, C). From this last mycelium the aecidium 'fruits first described develop. {a) The life-cycle, as above given, is apparently abridged in some of the Uredinese. The secidium and uredo stages are merged into one, or either the first or second is entirely wanting. This appears to be the case in Phragmidium, Oymnosporangium, Melampsora, etc. (6) With most of tlie species it happens that the secidiospores (conidia) develop upon one host, and the uredospores and teleutospores upon an- other. This alternation, which is termed by De Bary hetermcism, has added very much to the difficulty of the study of these fungi, and pos- sibly the apparent abridgement of the life-cycle above mentioned may in some instances be only an obscure heteroecism. (c) Thus far the sexual organs have not been discovered ; Sachs* argues that they must precede the secidiospores, and that the aecidium fruit is in all probability the result of a sexual act. He bases his
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