3o6 
THALLOPHYTES. 
developes sexual organs, and that, as the result of fertilisation, a structure is produced 
which is quite different from the mycelium, a fructification, which, except in the 
simplest forms of these Fungi, consists of an aggregation of numerous hyphse, and 
which presents great varieties of form. These fructifications are in many species 
small in proportion to the mycelium, and appear to be merely fruits developed 
upon it ; in other cases, however, they continue to grow vigorously for some time, 
and attain a considerable size, obtaining their nourishment independently. Under 
these circumstances they appear to be independent plants, or, according to our 
modes of expression, to be alternate generations destined to produce true spores 
in usually very large numbers. The spores thus formed within a fructification (car- 
pospores) are in these cases, as also among the Algae, extremely different if not in 
their size at any rate in their form and other properties, from the conidia produced 
asexually on the mycelium. When the fructification is of considerable size it is 
commonly regarded as being the whole Fungus, just as a Horse-tail or a Fern 
is thought to be the entire plant, although the insignificant prothallium is an essen- 
tial phase of the life-cycle of each of the latter. The mycelium, like the prothallium, 
is only the first stage of development, or, as it may be termed, the sexual generation 
(oophore), whilst the fructification corresponds to the fully-developed Horse-tail or 
Fern (sporophore). In those cases in which the fructification remains comparatively 
small and is nourished by the mycelium until maturity, a considerable similarity of 
habit becomes apparent between the Fungus and a Moss, for the sexually produced 
fructification of a Moss also derives its nourishment from the vegetative body of 
the first generation. 
Like that of the Florideae, the Characese, and the Coleochseteae, the fructification 
of a Fungus consists of two essentially distinct parts, namely, of a sterile portion, 
which is usually relatively large, and in some of the larger fructifications is by far the 
larger, and of a fertile portion in which, sooner or later, spores are formed. In the 
simpler forms the sterile tissue is merely an investing membrane which surrounds 
the spore-producing portion, but in larger and more complex fructifications, like those 
of Penicillium and Tuber, the sterile tissue is a compact mass into which the hyphse 
which are to produce the spores penetrate, and within which they obtain nourish- 
ment and further ramify. A still higher degree of independence is attained by the 
sterile portion when the fertile hyphae contained within it do not immediately give 
rise to spores but undergo a period of inactivity. Under these circumstances the 
fructification is, during the period of rest which may extend over weeks or months, 
simply a mass of tissue, which undergoes further development only when, under 
favourable circumstances, the contained fertile hyphae produce spores. An inactive 
fructification of this nature is termed, at the suggestion of Brefeld who carefully 
studied these phenomena in Penicillium, a sclerotiwn. 
When the formation of spores commences in the fructification, the fertile hyphae 
may either grow towards the exterior and form the spores at the surface, when the 
fructification is said to be gymnocarpous^ or they form the spores quite in the interior 
of the mass of sterile tissue, the outer layer of which then usually constitutes a firm 
cortex, the peridium, when the fructification is said to be angiocarpous. When 
numerous fertile hyphae form a coherent layer on the surface of the fructification, 
such a layer is termed a hymenium ; if, however, there is developed within the peridium 
