CARPOSPOREM. ' 315 



already exist become further developed. This development consists in the division 

 of the filaments into very numerous cells, which expand and thus form a coherent tissue. 

 The further extension of the ascogenous filaments is first diminished and then arrested 

 by the gradually increasing coherence of the investing cells, and they are seen, in 

 a median section, as thick hyphae running concentrically. After this formation of 

 tissue has taken place an expansion of the cells, which is not uniform throughout, 

 takes place, so that they attain six or eight times their previous size, and then their 

 walls become much thickened. This thickening begins simultaneously at two points, 

 internally, in the ascogenous hyphae, and externally, in a zone which is separated from 

 the periphery by a few layers of cells. 



* The fructification, now free from the mycelium, is of the size and colour of a 

 grain of coarse yellow sand. It is a sclerotium, consisting of from two to four peri- 

 pheral layers of cells elongated tangentially, of a yellowish-brown colour, and internally 

 of large cells arranged radially which become smaller towards the interior. Between 

 these run the firm ascogenous hyphae appearing like much-branched passages in the 

 tissue. 



* The sclerotia may be preserved in the dry state for as long as three months without 

 losing their vitality. If they are placed upon moist blotting-paper, a further development 

 of the ascogenous hyphae takes place within six or seven weeks. They again acquire the 

 appearance of living hyphae, and become divided into numerous cells, each cell being 

 capable of producing a branch which, at its first appearance, divides into a thick and 

 a thin filament. The thick filaments are concerned in the development of the spores, 

 whereas the thin filaments, which are but slightly branched and without septa, cause the 

 absorption of the surrounding tissue and supply the thick ones with nutriment. The 

 thick filaments form numerous closely-placed lateral branches immediately behind their 

 apices, a septum being formed between each pair. These branches form a series of asci, 

 each of which contains eight spores. 



' The result of further development is that the whole internal sterile tissue is absorbed, 

 the brown external layers alone remaining; the ripe asci together with the hyphae bearing 

 them and the nutrient filaments also disappear, so that finally, in six or eight months, 

 the sclerotium, although it has not altered in external appearance, has become converted 

 into a vesicle filled with a dense mass of countless spores of a bright yellow colour. 



' When seen under favourable circumstances each ascospore gives rise to a mycelium 

 quite similar to that developed from a conidium, which bears the characteristic conidio- 

 phores, each one of which can be genetically traced through the filaments of the mycelium 

 to the individual spores. 



* If, in consequence of desiccation, of a too advanced maturity, or for any other 

 reason, the sclerotia lose their capacity for growth, that is, if the ascogenous filaments 

 within them have lost their vitality, certain cells of their tissue may still be capable of 

 germinating. The hyphae springing from them come to the surface through fissures in 

 the sclerotium, and proceed to form the ordinary conidiophores. In this process the 

 physiological difference between the ascogenous filaments and the tissue surrounding 

 them, which amounts to a perfect contrast, becomes more definitely manifest.' 



The similarity of structure presented both by the ripe and the unripe fructifications 

 of PenicilUum with young and mature Truffles makes it at once evident that Penicillium 

 belongs to the Tuberaceae, and suggests that the formation of the fruit of the other 

 members of this group takes place in the way so fully described with reference to 

 Penicillium. Tulasne's ^ figures, especially that of Elaphomyces Leveillei, represent the 

 ascogenous filaments within the sterile tissue of the Truffles, and Brefeld observed them 

 again in Tuber rufum. The well-known yellow bands of hyphae correspond to the asco- 



* Tulasne, Fungi hypogsei, Paris 1862. [See also Reess, Parasitismus von Elaphomyces gramt' 

 tus, Sitzber. d. phys. med. Soc. zu Erlangen, 1880.] 



