264 THALLOPHVTES. 



a broad cake as in the * flowers of tan,' or weak ascending outgrowths which gradually 

 assume the form of the mature fructification, usually a stalked spherical or club- 

 shaped body, or a spiral tube ^, the growth of which is generally completed in a few 

 hours. It has already been mentioned that the ripe fructification is usually sur- 

 rounded by a firm wall, and that it often contains the so-called capillitium, in the 

 interstices of which lie the numerous spores. Neither the wall of the fructification 

 nor the capillitium is composed of cellulose, nor is the fruit-stalk, which is usually 

 hollow; it must rather be supposed that the substance of the Plasmodium, after it 

 has already assumed the external form of the fructification, becomes differentiated 

 into two distinct substances, one of which becomes hardened in various ways into 

 pellicles, tubes, and solid threads, and thus forms the stalk, the wall of the fructifica- 

 tion, and the capillitium, while the rest of the protoplasm, which has the capacity 

 of further development, breaks up into small round portions which become invested 

 with cell-walls and thus form the spores. The substance of the wall and of the 

 capillitium corresponds, therefore, as Brefeld has pointed out, to the mass capable 

 of swelling which fills up the space between the conidia in the conidiophore of the 

 Mucorini. In the process of free cell-formation also by which the ascospores of the" 

 Ascomycetes are produced, there often remains within the ascus a considerable portion 

 of its contents which is obviously not adapted to enter into the composition of a spore 

 capable of germination. 



In the differentiation of the protoplasm of the Plasmodium into spores and into 

 those portions (capillitium and wall of the fructification) which take no part in the 

 further development, other portions of the contents which are useless for purposes of 

 reproduction also become eliminated, and especially lime, which is often excreted in 

 large quantities in the form of fine granules of calcium carbonate, and the yellow sub- 

 stance which coats in loose flakes the fructification of the ' flowers of tan.' 



It must be added in conclusion that under favourable vital conditions both the 

 separate zoogonidia and the young or old plasmodia pass into a resting-state, the former 

 simply becoming invested by a cell-wall, the latter becoming transformed into masses 

 of cells'^. 



B. Conjugation takes place bet'ween stationary cells. 



In the Zygomycetes^ the vegetative body, which, as in all Thallophytes des- 

 titute of chlorophyll (Fungi), is termed the mycelium, consists of a ramified hollow 

 tubular cell (Fig. 174 B, m), in which septa only appear when it is fully mature and 

 ready for sexual or non-sexual propagation. The ramifications of this mycelium all 

 originate from a single germinating filament which is developed from a non-sexual 

 reproductive cell (conidium), and may, in the course of a few days, cover with a 



^ The term ^thalium is given by Rostafinski to those large fructifications produced by the co- 

 alescence of several simple ones, and which are therefore syncarps, as in the case of ' flowers of tan.' 



2 On the Chytridinese, which are perhaps allied to the Myxomycetes, see Braun, Abhandl. der 

 Berliner Akad. 1856, p. 22. — De Bary and Woronin, Berichte der naturf. Gesellsch. in Freiburg, 1863, 

 vol. III. Heft 2. — Woronin in Bot. Zeit. 1868, p. 81. [Sorokin (Bot. Zeit. 1874) has discovered in 

 Zygochytrium a process of conjugation resembling that of Mucorini, and in Tetrachytrium a con- 

 jugation of zoogonidia. Pfitzer (Monatsb. d. Acad, d, wiss., Berlin, 1872) includes Chytridtacece with 

 all the CoeloblastcB destitute of chlorophyll in one group, the Phycomycetes. Sorokin suggests the 

 name Siphomycetes for this, of which Amcehidium (Cienkowski, Bot. Zeit. 1861) is to be regarded as 

 the simplest form.] 



3 Brefeld, Botanische Untersuchungen liber Schimmelpilze, Heft i, 1872. — Van Tieghem, Re- 

 cherches sur les Mucorinees, Ann. des Sc. Nat., ^^ ser., 1873, vol. XVII, and in the French translation 

 of this work, p. 336 et seq. [Quart. Journ, Micr. Soc. 1871, pp. 49-76. — Ann. des Sc. Nat., 

 6® ser,, vol. I, 1875. p. i,] 



