JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATES IV, V, 

 Illustrating Dr. Lindsay's paper on the Genus Abrothallus."^" 



PLATE IV. 



I'ig. 

 1. — Portion of furfuraceous thallus of Parmelia saxatilis, bearing both 

 Abrothallus Smithii and A. oxysporus. 



a. A. Smithii — showing apothecia and intermixed pycnides. The 



portion of thallus on which it is parasitic diifers in colour and 

 other chai'acters from the ordinary thallus of P. saxatilis : it is 

 becoming globose from the curling of the margins and the super- 

 position of squamules or lobes. 



b. A. oxysporus in its young state. The squamules are more flat- 



tened, or concave, and simple than those habited by A. Smithii. 



c. A young and simple squamule, bearing only the spermogones of 



A. oxysporus. 



d. B,udimentary, as yet sterile, squamules. The black-fibrillose nature 

 of the under surface may be observed. 



e. Ordinary laciniai of P. saxatilis, showing their retuse extremities 



and the black-fibrillose under surface. 

 2. — Portion of thallus bearing A. Smithii, magnified. 



a. Mature apothecia. 



b. Young emergent apothecia causing Assuring of the cortical layer of 

 the thallus. 



c. Pycnides. 



d. Cyphelloid foveolse (produced by the falling out of the apothecia) 

 with raised dark margins. In one, the medullary tissue thus 

 exposed is seen to be white; in the other, red. 



e. Black-fibrillose under surface of thaUus. 



f. Fissure showing rusty red medullary tissue (common in Highland 



specimens). 

 3. — Section of young apothecia of A. Smithii, showing their mode of 

 evolution from, and relation to, their matrix. 



a. Young apothecium covered by a veil of the cortical tissue of 



matrix. 



b, c, d. Young apothecia gradually emerging through cortical layer. 

 4. — ^Section, showing mature apothecia a, b, and foveola c. 



a. Globose. 



b. Somewhat deplanate. 



r. Urceolate foveola left by falling out of an old apothecium. 

 .5. — Section, showing relation of the pycnides to the apothecia. 

 a. Mature apothecium. 

 fj. Mature pycnidis. 



c. Young or non-developed pycnidis. 



* The observations, from which the illustrations of minute structure were 

 drawn, were made chiefly under power 380 of a Nachet's microscope. 



