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.