CHAPTER I. HISTOLOGICAL CHARACTERISTICS. 5 



latter it is possible to give certain rules in individual cases ; as a rule the sprouts may 

 arise simultaneously at several spots in the mother-cell, or one after another from the 

 same spot. If all the generations of sprouts continue united to one another, it is 

 obvious that their combination simply forms an irregularly branched hypha, which is 

 distinguished from ordinary segmented hyphae only by the constriction at the narrow 

 point of insertion of the sprout-cells. This i i in fact the condition in which the cells 

 remain as long as they are not disturbed ; but eventually the full-grown sprouts 

 separate easily from one another, and a slight movement leaves only isolated sprouts 

 or small aggregates of them. 



The second exception is found in those simplest forms of the Chytridieae, in 

 which the entire thallus consists of a single round cell which ultimately produces 

 spores ; the less simple species of this group are allied by their structure to the 

 unicellular Filamentous Fungi described in sections XLVI-L. 



The Laboulbenieae may perhaps be reckoned as a third exception, but their 

 character is still very imperfectly known (see Division II). 



The view given above of the structure and growth of the thallus of the 

 Fungi has been already distinctly indicated in Ehrenberg's Epistola de Mycetogenesi 

 (Nov. Act. Acad. Nat. Cur. X) ; it is also clearly expressed in Vittadini's Monogr. 

 Lycoperdineorum (Mem. Acad. Turin. Ser. II, V, p. 146, 1841); and the views of 

 later writers (Montagne, Esquisse organographique, &c. sur les champignons, Paris, 

 1841, German edition, Prague, 1844, and Schleiden, Grundz. 3rd edition, II, p. 34) 

 are in accordance with it. Schleiden, and Unger after him (Anat. u. Physiol. d. 

 Pflanzen, p. 149), call the weft of distinct hyphae felted tissue, ' tela contexta.' Thoroughly 

 to establish and work out this view required fresh anatomical investigations, and to 

 these Bonorden and Schacht have given the chief impulse and contributed the first 

 more important materials. See Bonorden, Allgem. Mycologie, Stuttg. 1851, and 

 Schacht, Die Pflanzenzelle, p. 134. 



On the clamp-connections see Hoffmann in Bot. Ztg. 1856, p. 156 ; Tulasne, Carpol. 

 I, 115 ; Bail in Hedwigia, I, 96, 98, &c. ; Brefeld, Unters. iiber Schimmelpilze, III, 

 especially p. 17 ; Eidam in Cohn's Beitr. z. Biol. Bd. II, 229. 



The distinction of pseudo-parenchyma or apparent parenchyma was introduced 

 by myself in the first edition of this work. The term may be retained as it has become 

 familiar ; but it should be remembered, that it ought only to be used to indicate the 

 appearance of the close short-celled tissue of the Fungus with reference to the ordinary 

 conformation of the parenchyma of the higher plants. If the latter tissue is charac- 

 terised not, as is most usual, by the form of its cells, but by their structure and by 

 the functions indicated by their structure, then the pseudo-parenchyma is neither 

 more nor less to be compared with it than any other aggregate of cells in the Fungus 

 which serves for metabolism. 



The term Sprouting Fungus may be used as a general expression for the growth- 

 form which it designates. As the Saccharomycete with this form of growth which has 

 chiefly come under consideration is yeast, the term Yeast-fungus has usually been 

 employed instead of Sprouting Fungus ; but this leads to confusion, and the word Yeast- 

 fungus should not be used for the growth-form, but should be confined to the special 

 cases to which it is suited. 



The Schizomycetes will be described in the third part of this work. 



SECTION II. The cells of the Fungi agree in all important points with the 

 cells of other plants as regards structure, growth, and mode of division. 



The protoplasm, which in most cases fills uninterruptedly the interior of the 

 young cell, encloses in the full-grown cell of the Fungi, as of other plants, one or 



