414 



DIVISION III. MODE OF LIFE OF THE FUNGI. 



Thwaites was the first to describe 1 . Neither changes of structure nor premature 

 death have been observed in the algal cells on account of this attachment to the 

 hyphae. But the effect of the Fungus on the Algae is shown in a very remarkable 

 manner by the formation of a thallus of a fixed shape, which in some species is of 

 comparatively large size and has a progressive marginal growth, while the gelatinous 

 colonies of Gloeocapsa which are not attacked by the Fungus have a very indefinite 

 shape and are only loosely connected together. 



6. We conclude this account of the Lichens with a special consideration of those 

 which are formed with Hymenomycetous Fungi, a mode of proceeding which 

 is not indeed consistent with the arrangement hitherto adopted but which will be found 

 to conduce to perspicuity. The few species of the kind that are known belong to the 

 tropical zone and are distributed among the genera Cora, Fr., Rhipidonema, Matti- 

 rolo, Dictyonema, Mont., and Laudatea, Johow. They grow on dead parts of plants 

 and are attached to them by a copious growth of rhizoids or mycelium. Cora Pavonia, 



FIG. 180. a, b Thyrea pul-vinata, Mass, a vertical longitudinal section through the margin of the thallus b groups 

 of Algae, c Synalissa sp. (Pltctopsora botryosa. Jack, Leiner and Stitzenberger, Krypt. Bad. Nr. 301), portion of a thin 

 transverse section through a small lobe of the thallus. The surface of the gelatinous substance which is violet -red in nature 

 is shaded in the figure. Circumference of a inagn. 90 times, the other parts diagrammatically represented, f> magn. 390, 

 c 720 times. 



Fr. developes its thallus in the form of a flat semicircular fan resembling Stereum or 

 Thelephora (see p. 53) with marginal progressive growth. The thallus consists of 

 a loose air-containing weft of stout hyphae without evident differentiation into 

 medullary tissue and rind; its middle layer contains an abundance of groups of 

 Chroococcus-cells closely surrounded and embraced by branches of the hyphae. 



The thallus of Dictyonema and Rhipidonema, of similar construction to that of 

 Cora, is constructed out of filaments of Scytonema, which are attacked by the hyphae 

 of the Fungus, as in Ephebe and Ephebella, but by greater numbers of them, and 

 are thus taken up into a thallus-tissue formed of hyphae only. Johow's Laudatea 

 spreads over the substratum like a crustaceous Lichen, being attached to it by a 

 close mycelial weft, and winds its hyphae round Scytonema-filaments on the free 

 surface in the manner of Ephebe. 



Hymenomycetous sporiferous layers (see page 300) with numerous paraphyses 

 and comparatively few four-spored basidia are formed on the under side of Cora and 

 Dictyonema and on the free surface of Laudatea ; in Cora in the form of broadly 



1 Ann. and Mag. of Nat. Hist. ser. a, vol. Ill (1849). 



