TJw. Lichens of Victoria. 143 



and contain cells or granula gonima. Their functions are 

 unknown. Soredia are powdery protrusions of gonidia and 

 I >f portions of the interior through the surface of the thallus. 

 In some species, the npothecia are often conv^erted into 

 soredia and are sterile. This formerly constituted a genus 

 Vrriolaria, from which this formation is styled vaviolarioid. 

 The surface of the thallus is often roughened by minute 

 tlialline excrescences, which formerly gave rise to a genus 

 Isidium, by which name this formation is still distinguished. 

 The obsolete genus Lepraria was formed of lichens whose 

 thallus is s'terile and pulverulent. The obsolete genus 

 Spiloma has been foinid to consist of certain small fungi 

 parasitic on lichens. Various other foreign growths are 

 occasionally detected on tneir thallus and apothecia. Some- 

 tijnes minute alga?, or fungi, or portions of mosses will come 

 into view under the microscope; but their structure is 

 exidentl}' very different from that of the lichen with which 

 they are found. 



2. — The Usks of Lichens. 



Their chief design in nature seems to be to- form a 

 vegetable soil for the growth of higher plants. It is 

 lemarkable that no ])oisonous principle has ever been 

 found in any species of lichen ; yet, with the exception 

 oi a few kinds, they are seldom eaten by animals. Snails 

 devour them, and there are microlepidopterous larvae which 

 feed upon them. On a coi-al island in the Indian Ocean, 

 I found lichens with the traces of the claws of crabs, which 

 had evidently sought nourishment from them, especially 

 from their apothecia. 'J^he omnivorous Acarus destructor 

 seems to infest lichens, both in the field and in the herbarium. 

 .Some species afford nourishment to the higher animals. 

 What is called the reindeer moss is a lichen, and is well- 

 known as the chief food of the reindeer in Lapland. There 

 are also species in other lands, which are useful as fodder for 

 domestic animals. Even human beings occasionally use 

 some kinds for food, others are employed for medicine, and 

 others again have proved valuable for the dyeing of cloth. 



3. — The Geographical Distribution of Lichens. 



The growth of lichens in Victoria depends chiefly on the 

 moisture of the various districts of the colony. On the 



