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Pub. Paget Sound Biol. Sta. Vol. 2, No. 50 



found being cladonias. The genus Parmelia and the genus Peltigera rank 

 next in representation in this collection, six species of each having been 

 found. As both genera comprise large and conspicuous foliaceous species 

 they would naturally be among the first to attract attention. 



The genera known as Lecanora and Lecidea comprise more species 

 than any other lichen groups, but as the great majority are relatively 

 quite inconspicuous bark and rock dwellers, it is perhaps only to be ex- 

 pected that but few species would be found in a reconnaissance of this 

 character. Undoubtedly the region includes many more than the four 

 species of Lecanora and two of Lecidea which were collected. 



The number of endemic species in southeastern Alaska is very small 

 and this is only what is to be expected. A lichen is not a species in the 

 sense in which we speak of an oak, a maple, a Spirogyra, or an Agaricus. 

 It is not a homogeneous unit, developed from an egg cell fertilized by a 

 sperm cell from the same kind of an organism. There is therefore no 

 inheritance in the ordinary sense, since there are no chromosomes to carry 

 over the specific peculiarities of a given kind of lichen and accordingly 

 there is no Mendelian principle involved, no dominant and recessive char- 

 acters to be juggled about in the chromosomes. 



A lichen is what one might call a physiological species, the result of 

 the interaction of a fungus upon an enslaved alga, modified by the en- 

 vironment, and therefore in most respects not comparable to what is un- 

 derstood by the term "species" in most other groups of organisms. Their 

 propagation is, in general, by soredia and by fragments detached and 

 blown away. Soredia are minute masses of entangled algal cells and fun- 

 gus threads, which form on the surface of many lichens. These powdery 

 masses are widely distributed by the wind, and when they alight in favor- 

 able conditions develop into a thallus like the one from which they were 

 formed. A large number of lichens have no other means of reproduction. 



Where conditions are relatively uniform over great areas we find very 

 few endemic species, because with these vegetative forms of reproduction 

 it is difficult for considerable variation to arise under such conditions. 

 It is only in regions of geographic isolation and with strongly diverse 

 environmental factors, that Ave find a considerable number of endemic 

 forms specifically distinct from those of continental distribution in the 

 temperate regions of Europe and America. 



As southeastern Alaska shares its climatic features with a very con- 

 siderable area and is not greatly isolated, we may reckon upon the dis- 

 covery of but few new species there, however much we may extend our 

 knowledge of its lichen flora. 



