Fungi: Their Nature and Uses

by M. C. Cooke

The brothers Tulasne have made us acquainted with a greater number of instances amongst the Sphæriacei in which multiple organs of reproduction prevail. Very often old and decaying individuals belonging to species of Boletus will be found filled, and their entire substance internally replaced, by the threads and multitudinous spores of a golden yellow parasite, to which the name of Sepedonium chrysospermum has been given. According to Tulasne, this is merely a condition of a sphæriaceous fungus belonging to his genus Hypomyces.[I]

The same observers also first demonstrated that Trichoderma viride, P., was but the conidia-bearing stage of Hypocrea rufa, P., another sphæriaceous fungus. The ascigerous stroma of the latter is indeed frequently associated in a very close manner with the cushions of the pretended Trichoderma, or in other cases the same stroma will give rise to a different apparatus of conidia, of which the principal elements are acicular filaments, which are short, upright, and almost simple, and which give rise to small oval conidia which are solitary on the tips of the threads. Therefore this Hypocrea will possess two different kinds of conidia, as is the case in many species of Hypomyces.

A most familiar instance of dualism will be found in Nectria cinnabarina, of which the conidia form is one of the most common of fungi, forming little reddish nodules on all kinds of dead twigs.[J]

Fig. 104.—Twig with Tubercularia on the upper portion, Nectria on the lower.

Almost any small currant twig which has been lying on the ground in a damp situation will afford an opportunity of studying this phenomenon. The whole surface of the twig will be covered from end to end with little bright pink prominences, bursting through the bark at regular distances, scarcely a quarter of an inch apart. Towards one end of the twig probably the prominences will be of a deeper, richer colour, like powdered cinnabar. The naked eye is sufficient to detect some difference between the two kinds of pustules, and where the two merge into each other specks of cinnabar will be visible on the pink projections. By removing the bark it will be seen that the pink bodies have a sort of paler stem, which spreads above into a somewhat globose head, covered with a delicate mealy bloom. At the base it penetrates to the inner bark, and from it the threads of mycelium branch in all directions, confined, however, to the bark, and not entering the woody tissues beneath. The head, placed under examination, will be found to consist of delicate parallel threads compacted together to form the stem and head. Some of these threads are simple, others are branched, bearing here and there upon them delicate little bodies, which are readily detached, and which form the mealy bloom which covers the surface. These are the conidia, little slender cylindrical bodies, rounded at the ends.

Passing to the other bodies, which are of a deeper colour, it will soon be discovered that, instead of being simple rounded heads, each tubercle is composed of numerous smaller, nearly globose bodies, closely packed together, often compressed, all united to a base closely resembling the base of the other tubercles. If for a moment we look at one of the tubercles near the spot where the crimson tubercles seem to merge into the pink, we shall not only find them particoloured, but that the red points are the identical globose little heads just observed in clusters. This will lead to the suspicion, which can afterwards be verified, that the red heads are really produced on the stem or stroma of the pink tubercles.

Fig. 105.—Section of Tubercularia. c. Threads with conidia.[K]

A section of one of the red tubercles will show us how much the internal structure differs. The little subglobose bodies which spring from a common stroma or stem are hollow shells or capsules, externally granular, internally filled with a gelatinous nucleus. They are, indeed, the perithecia of a sphæriaceous fungus of the genus Nectria, and the gelatinous nucleus contains the fructification. Still further examination will show that this fructification consists of cylindrical asci, each enclosing eight elliptical sporidia, closely packed together, and mixed with slender threads called paraphyses.