T H !•: A M i: R I C A N B OTA N I ST 7Z 



lias since heci mu! aUaclK'd to a very (liffcrcnt ^^roiip of plants 

 of our Southwest throiij^di an error of old Gerarde. author of 

 the "Great Herbal". 



The Anomalous Lichkx. — The lichen is the only living 

 object in the world that is entirely vegetable without being a 

 plant! In the vegetable kingdom new individuals come into 

 existence as the result of the union of an egg and a sperm 

 derived from plants like themselves, but the lichen has no 

 parents. It does not grow from a fertilized Qgg and does 

 not conform to our ideas of a species. Practicallv evervboch- 

 is aware thai lichens are composed of two \q\-\ dilferenl 

 kinds of plants — an alga and a fungus — which live in partner- 

 ship and from v. hat might, by some stretch of our definitions, 

 be described as a physiological species in contradistinction to 

 the more usurd kind. In this associ.'ition of alga and fungus 

 a new plant-b(^dy is formed that is cpu'te different in appear- 

 ance from either member of the partnership when growing 

 alone. The fungus partner in the lichen forms spores whicli 

 may develop into new fungus plants but if they come into 

 contact with the right kind of algae they produce lichens. 

 A lichen once formed reproduces vegetatively l)v means of 

 soredia which consist of alga cells entwined by strands or 

 the fungus. On many lichens one may find tiny plate-like 

 projections heaped with these minute packages of fungus and 

 alga ready to be blown away by the wind. The lichen is 

 particularly resistent to the influences that hinder the growth 

 of other plants and in consequence is often the only form 

 of life present in deserts, on mountain tops and other inhos- 

 pitable places. Lichens are also among the most variable of 

 living things. They range in form from microscopic dots on 

 exposetl rocks to crustlike masses, leaf\- thalluses or even 

 bushy forms. They are most luxurious, of course, in the 



