414 DIVISION III.—MODE OF LIFE OF THE FUNGI. 
Thwaites was the first to describe’. 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 notindeed 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,5 Thyrea pulvinata, Mass. @ vertical longitudinal section through the margin of the thallus, 4 groups 
of Algae. c Synalissa sp. (Plectopsora 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 gel which is violet-red in nature 
is shaded in the figure. Circumference of a magn. go times, the other parts di icall p! d, 6 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. 2, vol. III (1849). 
