3o6 THALLOPHVTES. 



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 hyphae, 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 Algse, 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 iriaturity, 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 Characeae, and the Coleochaeteje, 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 hyphae 

 which are to produce the spores penetrate, and within which they obtain nourish- 

 ment and further ramify. A still ilfgher 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 sclerotiuin. 



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 hymenimn ; if, however, there is developed within the peridium 



