114 PLANT-LIFE 



pared nutrient solutions in the laboratory, so it would 

 seem as if the Fungus can exist independently of the 

 Alga ; but, it must be noted, we have evidence of only 

 one species living apart from its Alga in a state of 

 nature. Experimenters have been able to synthetize 

 Lichens by rearing spores of Lichen-fungi on free Algae. 

 The Algae which enter into the Lichen partnership are 

 relatively few in species. They are representatives of 

 the Blue-green Algae, and some members of the Green 

 Algae, the Chlorophyceae. On the other hand, the 

 Fungi entering into the structure of Lichens are very 

 numerous. As the Algal-partners are few in relation to 

 the Fungal-partners, it is patent that the same species 

 of Alga may join with several species of Fungi, other- 

 wise there would not be sufficient kinds of Algae to go 

 round. 



Seeing that the Fungus element in a Lichen is pre- 

 dominant, and that the Algal-partners can exist inde- 

 pendently, and, moreover, be identified as species com- 

 monly living by themselves, it is now deemed proper to 

 classify Lichens in accordance with the nature of their 

 Fungal constituents. This position seems fully justified 

 when we realize that it is always the Fungus-partner that 

 produces the fructifications. The Algae multiply by 

 division. The majority of the Fungi entering into 

 Lichen-partnership belong to the Ascomycetes, an Order 

 of Fungi in which the spores are developed inside 

 tubular sporangia, called asci (Gr. askos, a leather 

 bottle). Never more than eight spores occur in a single 

 ascus. Further, most Lichen-Fungi belong to a Sub- 

 order of the Ascomycetes, yclept the Discomycetes — 

 distinguished by the fact that the ascus-bearing surface 



