2'^H THALLOPHYTES. 



CLASS IL 

 F U N G p. 



The structural element from which the thallome of Fungi is built up consists 

 of cellular filaments destitute of chlorophyll, endowed with apical growth, only rarely 

 branching dichotomously, more usually abundantly by lateral shoots. These ele- 

 mentary constituents of Fungi are called HyphcB. It is only in a single group of 

 Fungi — forming the transition from the Siphoneae among the Algae to the typical 

 Fungi — the Phycomycetes, that the hypha consists of a single undivided cell ; in 

 all other cases it is divided by transverse septa. The Hypha is thus usually 

 a branched row of cells destitute of chlorophyll wdth a growing apical cell which 

 divides transversely ; intercalary transverse divisions, however, also occur in the 

 cells. In the simplest forms, which have been termed Haplomycetes, including 

 however mere conditions of development of higher forms, the whole thallome con- 

 sists of a single hypha usually very much branched. The massive compact sub- 

 stance of many Fungi is formed by the aggregation of numerous hyphae having a 

 common growth ; the larger Fungi are, without exception, examples of this. The 

 hyphae either run parallel to one another, or their numerous ramifications are inter- 

 woven in the most various modes. If these textures are very dense and the 

 joints of the hyphse therefore short and thick, and of a polyhedral form from 

 pressure on opposite sides, the mass assumes the form of a parenchymatous tissue, 

 the origin of which from hyphae justifies its appellation of Pseudo-parenchyma. It is 

 especially developed on the surface of larger Fungi as an epidermal system. 



When the substance of a Fungus consisting of a number of hyphae grows in 

 length forming an apex at one point, this — as follows from what has been said — ' 

 can never take place by means of otte apical cell, but a certain number of hyphae 

 reach to the apex, where each lengthens by apical growth but in unison with its 

 neighbours. If the substance of such a Fungus spreads out in the form of a disc 

 growing at the margin, this is occasioned by the hyphae proceeding from a centre 

 lengthening radially and ramifying laterally in proportion to the growth of the 

 circumference. Ramification rarely occurs in Fungi of this kind (<?. g. in Clavaria 

 and Xylaria); and in this case the individual branches are always similar to one 



^ The most important works which include the whole class are Corda, Icones Fungorum, 6 vols. 

 Prag 1837-1S54. — Tulasne, Selecta Fungorum Carpologia, 3 vols. Paris 1861-1865. — De Bary, 

 Morphologic u. Physiologic der Pilze, Flechten u. Myxomyceten, Leipzig 1866. — The most im- 

 portant papers on single sections are cited below. — De Bary's Ueber Schimmel u. Hefe, Berlin 1869, 

 is also of general interest. [Berkeley, Outlines of British Fungology. London i860. — Cooke, 

 Handbook of British Fungi. London 1871.] 



