_Hypoxylon_ and _Ustulina_ have a cushion-like or crustaceous stroma.--_Xylaria_ has a club-shaped or branched stroma, often several centimetres high. _X. hypoxylon_ (Fig. 122) and _X. polymorpha_ occur on old tree stumps.--_Poronia_ grows on old horse dung, and has a conical stroma. Sub-Family 3. =Dothideales.= The _perithecia_ are always embedded in a _black stroma_, and are _not distinctly separated_ from it. The accessory forms of reproduction are: conidiophores, conidiocarps, and yeast-like conidia. The majority are parasites. One order. Order =Dothideaceæ=. _Phyllachora graminis_ produces scab-like patches on the leaves of the Grasses.--_Scirrhia rimosa_ grows on the leaf-sheathes of _Phragmites_.--_Rhopographus pteridis_ on _Pteridium aquilinum_. Family 4. =Hysteriales.= This family, like the following, has hemiangiocarpic ascocarps (_apothecia_). These are closed in the early stages, but when ripe _open_ in a _valvular manner_ by a _longitudinal fissure_; they are black, oblong, and often twisted. Some species are parasites, especially upon the Coniferæ. [Illustration: FIG. 123.--_Lophodermium (Hypoderma) nervisequium_: _a_ two leaves of _Abies alba_ seen from above with pycnidia; _b_ a leaf seen from the underside with apothecia; _c_ an ascus with ascospores. (× 500.)] [Illustration: FIG. 124.--Three leaves of the Red-pine with _Lophodermium macrosporum_: _a_ under side of the leaves with apothecia; _b_ a leaf from upper side with pycnidia. (× about 2.)] [Illustration: FIG. 125.--_Lophodermium pinastri_: _a_ leaves of _Pinus sylvestris_ with apothecia (nat. size); _b_ two paraphyses and an ascus with filamentous spores.] Order 1. =Hysteriaceæ.= _Hysterium pulicare_ upon the ruptured bark of many trees. Order 2. =Hypodermaceæ.= The species of _Lophodermium_ live upon the leaves of Conifers, and are the cause of their falling off (_blight_). _L. pinastri_ (Fig. 125), on the leaves of _Pinus_ and _Picea_; the leaves become red-brown and fall off; at first conidiocarps are formed, and later apothecia; _L. nervisequium_ (Fig. 123), on _Abies alba_; _L. macrosporum_ (Fig. 124), on _Picea excelsa_; _L. brachysporum_, on _Pinus strobus_. Order 3. =Dichænaceæ.= Order 4. =Acrospermaceæ.= Family 5. =Discomycetes.=