2388 Journal of Applied Microscopy 



2. Pick out some of the internal mycelium (capillitium) and after moisten- 

 ing with alcohol mount in water. Under high power draw some of the dichoto- 

 mously branched mycelium and some of the spores. Describe. How does this 

 plant obtain its nourishment ? 



XL. Liche7ies. Ascolichenes. 



Lichens grow on the bark of trees, on wooden fences, on rocks and on the 

 ground. The common forms may be collected and kept indefinitely in a dry 

 condition in wooden or paper boxes. Lichens are associations of fungi and 

 algae. They represent a condition of symbiosis known as helotism, i. e., the 

 fungus is a slaveholder, the algae are slaves. 



{(i) Parmelia caperata (L.) Ach. 



This lichen is of a light green color and is very abundant on trees and 

 fence boards and rails, forming large circular thalli often a number of inches in 

 diameter. 



1. Study the naked eye characters of the thallus. Draw a part of the thal- 

 lus, showing the margin. 



2. Soak the thallus in water and tease out a small piece on the slide with 

 needles. Study under high power. Notice two kinds of cells, colorless septate 

 hyphae, the lichen fungus, and green spherical cells, the lichen algae. Draw a 

 piece of the mycelium and some of the algai. To what group do the algae 

 belong ? How are the algae and the fungus hyphae arranged in the lichen thal- 

 lus ? 



3. Draw two or three algae, showing the manner in which the fungus grows 

 around the green cell to obtain its food. 



4. Vegetative propagation. The alga and the fungus each reproduces itself 

 in the manner peculiar to its species, but the lichen may also propagate itself 

 directly by means of little granular flakes produced on the upper surface of the 

 lichen thallus, known as soredia. Mount some of the granular material in water 

 and examine under low power ; notice in favorable specimens that the fungus 

 and algae are both present in the soredium. Draw and describe. 



(/>) Stida amplissima (Scop.) Mass. 



This is a foliaceous lichen of a light gray color which grows on the bark of 

 trees in forests. 



1. Soak the thallus in water and note the change in color of the upper sur- 

 face. Make a sketch showing the position of the brown disc-shaped or cup-shaped 

 apothecia. 



2. With a razor, cut free hand cross section of a piece of the thallus con- 

 taining an apothecium. Hold the piece between two strips of dry elder pith. 

 Mount the sections in water and under low power draw, showing the green algal 

 layer, the white layer and the position of the apothecium. 



3. Under high power study the hymenial layer of the apothecium. Draw 

 one of the asci containing spores. Describe. How many spores ? Draw a 

 single spore. Draw one of the paraphyses. 



(^) Endoca?-po)i miuiati/fu (L.) Schaer. 



This lichen with a rather leathery thallus is common on limestone, where it 

 may be obtained at any time of the year. 



1. Lay the thallus on the slide without a cover-glass and examine under low 

 power. Draw a part of the thallus, showing the pores which open into the peri- 

 thecia below. 



2. Cut cross-sections of the thallus and mount in water. Sketch under low 

 power, showing the algal and fungal layers and the perithecia. 



3. Draw one of the perithecia under high power ; also an ascus containing 

 spores. John H. Schaffner. 

 Ohio State University. 



