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I 



CHAPTER III. 



LEPRARIACEAE PSEUDOLICHENES. 



In this group I have temporarily classed those structures whose 

 position among lichens is uncertain, or which are perhaps not true 

 lichens. The principal genera occurring in the territory are 

 Lepra and AtnphiJoma ; of the former we have the representative 

 L. viridis Schaer., which is common everywhere, occurring on trees, 

 fences, and rocks in moist shaded places ; it is usually recognized 

 as Plcurococcus ( Protococcus) vulgaris ; upon closer examination it is, 

 however, found that it consists of an association of Plenrococcus with 

 the hyphal network of some fungus ; the fungal portion never produces 

 apothecia ; it is also found that in some instances the hyphae are al- 

 most entirely wanting ; it is, therefore, in all probability, a case of 

 contingent symbiosis (see Contingent Symbiosis). The structural 

 association of the hyphae with the algal cells is less intimate than in 

 true lichens (see Fig. 2, pi. i). The haustorial branches do not 

 form such a complete covering or network about the algae ; in no 

 instance have I noticed that the haustoria penetrate the alga. In 

 some instances Lepra develops a growth which to external appear- 

 ances resembles a typical crustaceous thallus ; it differs, however, 

 in the absence of layer-differentiations ; that is, algae and hyphae 

 are about uniformly intermingled ; it differs also in the fact that its 

 limitations of growth are not so fixed as in the true lichen thallus ; 

 it may spread over areas several yards in diameter, or it may cover 

 the entire side of a large tree-trunk. 



As to the origin of the hyphae nothing definite is known at pres- 

 ent. In general it is found that they are quite uniform in the structure 

 and size of the hyphal cells ; the filaments are much contorted and 

 twisted, and the new branches are formed very nearly at right angles 

 to the mother-branch. I am unable to state whether these hyphae 

 originate from spores (of fungi or lichens) or whether they are hy- 

 phal branches derived from some lichen or fungus growing in the 

 vicinity ; it is known that hyphae may grow to a great length under 

 suitable conditions. Such suitable conditions are no doubt supplied 

 by the algae which furnish the hyphae with an abundance of assimi- 

 lated food substances, thus enabling them to grow indefinitely ; 

 apothecia are not formed because of this hypernutrition. It is also 



