CRYPTOGAMS 415 



The highest development of the fructifications is exhibited by the Phalloideae 

 ( 82 ), of which Phallus impudicus (Stink-horn) is a well-known example. This 

 fungus is usually regarded as poisonous. It was formerly employed in a salve as 

 a remedy for gout. Its fructification recalls that of the discomycetous Morchella, 

 but it has quite a different manner of development. A fructification of this 

 species of Phallus is about 15 cm. high. It has a thick, hollow stalk of a white 

 colour and is perforated with pores or chambers. Surmounting the stalk is a bell- 

 shaped pileus covered with a brownish-green gleba which, when ripe, is converted 

 into a slimy mass (Fig. 364). When young the fructification forms a white, egg- 

 shaped body, and is wholly enveloped by a- double-walled peridium with an inter- 

 mediate gelatinous layer. Within the PERIDICM (also termed volva) the hyphal 

 tissue becomes differentiated into the axial stalk and the bell-shaped pileus, carry- 

 ing the gleba in the form of a mass of hyphal tissue, which contains the chambers 

 and basidial hymenium. At maturity the stalk becomes enormously elongated, 

 and pushing through the ruptured peridium raises the pileus with the adhering 

 gleba high above it. The gleba then deliquesces into a dropping, slimy mass, 

 which emits a carrion-like stench serving to attract carrion-flies, by whose agency 

 the spores embedded in it are disseminated. 



CLASS XV 

 Lichenes (Lichens) (. 8M1 ) 



The Lichens are symbiotic organisms ; they consist of higher 

 Fungi, chiefly the Ascomycetes, more rarely Basidiomycetes, and uni- 

 cellular or filamentous Algae (Cyanophyceae or Chlorophyceae), living 

 in intimate connection, and together forming a compound thallus or 

 CONSORTIUM. Strictly speaking, both Fungi and Algae should be 

 classified in their respective orders ; but the Lichens exhibit among 

 themselves such an agreement in their structure and mode of life, 

 and have been so evolved as consortia that it is more convenient to 

 treat them as a separate class . 



In the formation of the thallus the algal cells become enveloped 

 by the mycelium of the fungus in a felted tissue of hyphse (Figs. 365, 

 366). The fungus derives its nourishment saprophytically from the 

 organic matter produced by the assimilating alga ; it can also send 

 haustoria into the algal cells, and so exhaust their contents ( 84 ). 

 The alga, on the contrary, derives a definite advantage from its 

 consortism with the fungus, receiving from it inorganic substances 

 and water, and possibly organic substances also (cf. p. 234). From 

 the symbiosis entered into by a Lichen Fungus with an Alga, a 

 dual organism results with a distinctive thallus, of which the form 

 (influenced by the mode of nutrition of the independently assimilating 

 Alga) differs greatly from that of other non-symbiotic Eumycetes, 

 and rather resembles that of the Algae and Liverworts. 



The thalli of the Lichens exhibit a great variety of forms. 



The simplest Lichens are the FILAMENTOUS, with a filiform 



