[Illustration: FIG. 152.--Pear-leaf, seen from the under side, with “_Rœstelia cancellata_”: in different ages (_a_ youngest, _d_ oldest).] [Illustration: FIG. 153.--_Melampsora betulina_: _a_ uredospores; _b_ three contiguous teleutospores, one of which has developed a basidium with three basidiospores. (× 400.)] [Illustration: FIG. 154.--_Gymnosporanginum juniperinum_: _a_ a small leaf with three clusters of æcidia (nat. size); _b_ three conidia; _c_ two æcidiospores on one of which are seen the germ-pores; _d_ a portion of the wall of an æcidium; _e_, _f_ two teleutospores.] [Illustration: FIG. 155.--_Coleosporium senecionis_: _a_ Pine-leaves with æcidia (_Peridermium wolffii_) nat. size; _b_ an æcidiospore; _c_ a germinating æcidiospore; _d_ a chain of uredospores; _e_ a chain of teleutospores of which the terminal one has germinated and produced a basidiospore (_s_).] _Cronartium_ (Figs. 157, 159) has unicellular teleutospores united in numbers to form erect threads or columns; the uredospores are enclosed in a “peridium”; _C. ribicola_ (Fig. 157), on leaves of Ribes (especially Black Currants); its æcidia (_Peridermium strobi_, or _P. klebahni_) on the stems and branches of _Pinus strobus_ (Fig. 159), on which it causes great damage; _C. asclepiadeum_, on _Vincetoxicum officinale_; its æcidia (_Peridermium cornui_) on the stems and branches of _Pinus silvestris_. [Illustration: FIG. 156.--_Chrysomyxa abietis_: _a_ leaf of the Fir, with 5 clusters of basidiospores (× 4); _b_ branched rows of teleutospores springing from the mycelium (_m_).] [Illustration: FIG. 157.--_Cronartium ribicola_: _a_ mass of uredospores (× 50); _b_ an uredospore; _c_ a column of teleutospores (× 60); _d_ a small portion of the same more highly magnified, with a basidium and two basidiospores (_s_).] To the Fungi of which the æcidium is known, whilst the remaining forms are still undetermined, but which are without doubt heterœcious, belong _Æcidium elatinum_, which produces the enormous “witches’ brooms” and barrel-shaped swellings on stems and branches of _Abies alba_; and _Æcidium strobilinum_ (Fig. 158), which attacks Fir-cones, causing all the scales to become covered with clusters of æcidia opening by a lid. _Hemileia vastatrix_ destroyed the coffee plantations in Asia. [Illustration: FIG. 158.--_Æcidium strobilinum_: _a_ scale of cone of _Picea excelsa_, with numerous æcidia; _b_ æcidiospores arranged in a series; _c_ a cell of the peridium.] Order 2. =Auriculariaceæ.= The _long, transversely divided_ basidia bear laterally 4 _long sterigmata_ with basidiospores (Fig. 160 _B_) and are united to form an _hymenium_ on the surface of the fruit-body. Parasites or saprophytes.