CARPOSPOREm. 



r-1 



dense pulvinate masses (as in Usnea, Ramalina, E'vernia, Pbyscia, Parmelia^ Pertusaria, &c.). 

 In the heteromerous thallus the soredia appear in the gonidial layer; single gonidia, or 

 sometimes several together becoming woven over by branches of hyphae which cling 



Fig, 221. — A — D soredia of Usiiea barbata; A a simple sorediuiii, consisting of a gonidium covered with a web of 

 hyphae ; B a soredium, in which tlie gonidiuin has multiplied by division ; C a group of simple soredia, resulting from the 

 penetration of the hyphw between the gonidia ; D, E germinating soredia ; the liypliai are forming an apex of growth, and 

 the gonidia are multiplying ; i7-c soredia oi Physcia parietina; « with an envelope of pseudo-parenchyma ; * the envelope 

 producing rhizines ; c a young thallus formed from a soredium (after Schwendener, X 500). 



closely to them and form an envelope of fibres. The gonidia divide repeatedly, and each 

 daughter-cell is again woven over. This process is often repeated, the soredia accu- 

 mulate in great numbers in the gonidial layer, and finally rupture the cortex. After 



Fig. 222.— Examples of various Algre which act as the gonidia of Lichens (after Bornet) ; h in all cases is the hyjilia of 

 the Fungus, ajid^rthe gonidium. A, germinating spore s oi Physcia parietina, the hypha of which has attached itself to 

 Protvcocctis viridis; R, a filament ofScytonema invested by the hyphae oi Stereocajtloii ramnlosum; C, taken from the thallus 

 of the \Jichen, Pkysjna chalaf^amtm ; a branch of the hypha is penetrating into a cell of the Nostoc-filament (gonidium) ; 

 D, taken from the thallus of Synalissa symphorea, the gonidia are the Alga Glceocapsa; E, from the thallus oi Cladoma 

 Jttrcata, the gonidium {Protococcus) is invested by hyphae. 



escaping in this manner, the soredia can still further multiply outside the thallus; but 

 under favourable conditions either a single soredium or a mass of them grows out at once 

 into a new thallus (Fig. 221). Schwendener states that in Vsnea barbata this may occur 



