Y 
Frrest Parr. 
FUNGI, 
DIVISION I. GENERAL MORPHOLOGY. 
CHAPTER I. HISTOLOGICAL CHARACTERISTICS. 
Section I. The thallus, which in most Fungi is the whole body of the plant 
not serving directly as an organ of reproduction, begins as a tubular germ-cell 
(germ-tube, Keimschlauch) which, by continued growth progressing in an apical 
direction accompanied by repeated formation of lateral branches, developes into a 
branched body of cylindric thread-like form, the pa. Both growth and branching 
follow the laws which prevail generally in the vegetable kingdom. The branching is 
usually monopodial, in a few cases only it is dichotomous, as in Botryosporium, species 
of Peronospora, and some Mucorini. 
In some groups, especially the Saprolegnieae, Peronosporeae and the Zygo- 
mycetes, the thallus or hypha of the Fungus, like the thallus of the Siphoneae, is 
an unsegmented branched tubular cell up to the time when organs of reproduction 
are formed. But in the great majority of cases it becomes a branched row of cells 
owing to the incessant formation of transverse walls concurrently with the growth 
of the hypha at its apex. The segmentation either takes place only in the apical 
cell for the time being and at the place of insertion of the rudimentary branch, 
so that each branch is made up of an apical cell and segment-cells of the first order 
only, as in Penicillium? and Botrytis cinerea, or new intercalary partition-walls are 
formed in the segment-cells of the first order. 
In the more simple Fungi the branched hypha alone constitutes the thallus; 
such forms are termed Hyphomycetes, Filamentous Fungi (Fadenpilze), or 
Haplomycetes?. The body of the largest Fungi, the Mushrooms and Lichens of 
ordinary parlance, are also composed of hyphae, but their ramifications meet and 
cohere to form larger aggregates. Such a body, which appears as if formed by the 
union of Filamentous Fungi, may be termed a compound Fungus-body (zusam- 

1 Löw in Pringsheim’s Jahrb. VII. p. 473.—Brefeld, Schimmelpilze, II. p. 27. 
2 From the Greek word damAods, meaning simple. 
[4] B 
