CHAPTER V.—COMPARATIVE REVIEW.-—-ASCOMFCETES. 229 
produce a dense hymenium. The gonidia in the highest state of development are 
abjointed successively in long rows forming a close colourless mass which covers the 
cushion, each gonidium having the form of a bent cylinder 60 » in length and divided 
by transverse walls into several members (spore-cells), which may be as many as eight 
in number. Besides these there are some much smaller, but of similar origin, in which 
the number of members sinks to two. Each segment-cell of these gonidia may 
develope in a moist atmosphere into a branched hypha, from single branches of which 
‘fresh smaller gonidia are abjointed. If the mycelium vegetating in the tissue of the rind 
of the tree comes to lie exposed in a moist atmosphere, it sends out numerous branches 
into the air, and from these also countless small gonidia are abjointed. The size of all 
these small gonidia sinks by regular gradations to 1.5 u; they are all cylindrical and 
rod-like; those of medium size are divided by a transverse wall into two segments 
which often separate from one another; the smallest are undivided. All down to 
the size of 2 » can put out germ-tubes or may also multiply by sprouting. The very 
smallest have never been observed to put out germ-tubes, but they appear to multiply 
by division and fission and by sprouting. Lastly, gonidia of the smallest kind are also 
formed in great numbers by slender branches of: the mycelium in the interior of the 
tissue attacked by the Fungus. All germ-tubes, whether from gonidia or from asco- 
spores, can develope new fertile mycelia in the proper substratum, that is, in the living 
rind of a tree; it is doubtful whether the smallest gonidia can produce mycelia 
(see section LXXIV). There is also some doubt as to the true nature of certain acro- 
genously abjointed spores which occur on the sporocarp-bearing portions of the Fungus 
which we are considering; they appear to belong to parasites of Nectria, and it will be 
sufficient therefore in this place to refer the reader to Hartig and Tulasne. 
The development of Cordyceps with its great variety of forms will be described 
subsequently in Division III. 
The cycle of development of the one or perhaps two species included under the 
name of Pleospora herbarum is particularly rich in forms. These are found in dead 
and rotting herbaceous plants. The results which will be given here were obtained 
from plants cultivated in nutrient solutions on the microscopic slide. The mycelium 
forms (I) the Zerzthecia mentioned above with pluricellular compound ascospores : 
(2) gonidia of three kinds produced acrogenously on filiform gonidiophores, namely,— 
(a) bicellular or pluricellular spores resembling the ascospores, in general shape shortly 
cylindrical to roundish, with dark-brown thick membranes rough with fine points on the 
outside, named by Berkeley as a form-species in 1838 Macrosporium Sarcinula and 
therefore called by Gibelli and Griffini the Sarcinula-form ; they are usually produced 
singly at the end of the gonidiophore ; (6) the Alternaria-form, classed with the old 
form-genera Alternaria, Sporidesmium, Mystrosporium, and Polydesmus ; these are coni- 
cally pear-shaped pluricellular compound spores having a smooth light-brown membrane, 
and arising at the extremities of the hyphae in long and often branched rows (Fig. 34) ; 
(c) a form said by Bauke to be a microgonidial form, but of which he gives no further 
description; it is not the one known as Cladosporium herbarum and placed by 
Tulasne with Pleospora herbarum, for this, according to all later investigations, does 
not belong to this place at all and its genetic connection is uncertain: (3) pycnidia 
(see below, section LXXI, Figs. 118, 119) which appear as intercalary formations on 
branches of the mycelium. A piece of the hypha consisting of one or several cells 
swells in the same way as when a perithecium begins to be formed, and its cells 
divide at the same time meristematically and irregularly by walls inclined in every 
direction. By this process of growth a small-celled parenchymatous body is formed 
of many layers, which is round or irregularly elongated in shape and seldom more 
than o.2 mm. in size, often much less. This body is at first uniformly dense, but 
towards the end of its growth a central cavity is formed in it surrounded by the many- 
layered wall ; this cavity is produced by the cells of the central part ceasing to follow 
the growth of the outer parts in the direction of the surface and therefore separating 
