210 
W. J . Dowson , 
IV.— Detailed Examination of DERMATELLA PRUNASTRI Pers. 
The pycnidia, formerly thought to be a distinct fungus and 
called Sfhceronema spurium (Fr.) Sacc., are elongated conical-shaped 
structures 1—2 mm. long which arise in the cortex a little way 
below the cork layer. They consist for the most part of a hard 
pseudo-parenchymatous tissue deeply pigmented on the exterior. 
From the basal portion ramify numerous hyphse between the cortical 
cells. The upper distal part of the pycnidium is a narrow, short, 
hollow cylinder lined with the conidia-bearing hyphae, whilst the 
lower part of this columnar structure is composed of sterile tissue. 
The conidia are produced in enormous quantities and are small 
(20/xX 2*5/x), crescent-shaped, unicellular hyaline spores, often with 
a highly refractive globule placed at the centre (Fig. 3, A). This 
body on staining proved to be the nucleus. In a damp atmosphere 
the conidia are extruded in coiled threads from the pycnidia, which 
were found to be numerous in autumn and throughout January. 
The apothecia are small (•5—1*5 mm. in diam.), button-shaped 
bodies which are soft and slightly gelatinous in a damp atmosphere 
but hard and leathery when dry. The disc is provided with a narrow 
rim and is raised from the surface on a short thick stalk slightly 
embedded in the cortex. They are black in colour, and with the 
exception of the upper surface (hymenium) which is covered with 
asci and paraphyses, are composed of a pseudo-parenchymatous 
tissue. The asci are club-shaped (Fig. 3, B) and are surrounded 
by paraphyses which contain a dark coloured pigment in their 
upper portions which gives a blackish appearance to the hymenium. 
The paraphyses are branched and multi-septate (Fig. 3, B). The 
apothecia were not so numerous in January as in December. 
The ascospores are variable in shape and size, and may be 
crescent-shaped, straight or oval, from 10—20/x long and 5/t broad. 
These spores are filled with small globules of fat or glycogen to such 
an extent that the septa are rarely seen in unstained preparations 
(Fig. 3, C). In preparations stained in Delafield’s hsematoxylin or 
in Heidenhain’s iron-alum-haematoxylin, the septa are well seen 
and vary in number from one to four, the most usual number being 
two (Fig. 3, D). 
V. —The Mycelium in the Wood. 
Owing to the great amount of gum present in the diseased 
wood some difficulty was experienced in staining sections cut from 
such areas. The most useful stains proved to be Delafield’s haema- 
toxylin and the combination Methyl green and Congo red in watery 
