Orders 3–7. _Perithecia scattered or aggregated, situated from the commencement on the surface of the substratum. Stroma wanting._ Order 3. =Trichosphæriaceæ.= _Trichosphæria parasitica_ (Fig. 121), on _Abies alba_; _Herpotrichia nigra_ on _Picea excelsa_ and _Pinus montana_. [Illustration: FIG. 121.--_Trichosphæria parasitica_: _a_ a twig of _Abies alba_, with epiphytic mycelium; _b_ a leaf with mycelium and sporangia (magnified); _c_ a sporangium (× 60); _d_ an ascus with spores (× 550).] Order 4. =Melanommaceæ.= _Rosellinia quercina_ lives in the roots of 1–3-year-old Oaks, and destroys the plants. Order 5. =Ceratostomaceæ.= Order 6. =Amphisphæriaceæ.= _Strickeria obducens_ (Fig. 120) has brick-like spores, and lives aggregated on the hard branches of _Fraxinus_. Order 7. =Lophiostomaceæ.= Order 8. =Cucurbitariaceæ.= Perithecia tufted, _at first embedded, then breaking through_, often situated upon an indistinct _stroma_. Orders 9–13. _The perithecia remain embedded, and are only liberated by the casting off of the covering layers of the substratum. Stroma wanting._ Order 9. =Sphærellaceæ.= The species of _Sphærella_ have colourless, bicellular spores. They live upon the leaves of many plants, and develope spherical perithecia upon the fallen leaves. Order 10. =Pleosporaceæ.= The conidial-forms of _Pleospora herbarum_ and _P. vulgaris_ form a black covering on various plants, known as “smuts.”--_Venturia ditricha_ occurs on the underside of dry Birch leaves, and perhaps to this belongs the conidial-form, _Fusicladium pirinum_, which causes the “Rust spots” on Apples and Pears. Order 11. =Massariaceæ.= Order 12. =Clypeosphæriaceæ.= Order 13. =Gnomoniaceæ.= Perithecia, with peak-like aperture. _Gnomonia erythrostoma_ in the leaves of _Prunus avium_, which turn brown and do not fall in autumn. Orders 14–18. _Stroma generally well developed. The perithecia are embedded in the stroma, but when this is rudimentary, in the substratum._ Order 14. =Valsaceæ.= _Valsa._ Order 15. =Diatrypaceæ.= _Diatrype._ Order 16. =Melanconidaceæ.= Order 17. =Melogrammataceæ.= Order 18. =Xylariaceæ.= This order is the most highly developed of the Sphæriales. The _stroma_ arises on the _surface of the substratum_, which is generally dead or decorticated wood; it is well-developed, crustaceous, hemispherical or upright. In the younger conditions it is covered with a layer of conidia, and later on it bears the _perithecia_, arranged in a layer immediately _beneath its surface_. The ascospores are of a dark colour. Often also there are free conidiophores. [Illustration: FIG. 122.--_Xylaria hypoxylon_ (nat. size) on a tree stump: _a_ younger, _b_ an older stroma, both of which, with the exception of the black lower portion, are covered with white conidia; _n_, spot where the perithecia are developed; _c_ an old stroma with upper part fallen off; _d_, _e_ large branched stromata; _k_ conidia.]