Journal 



OF THE 



NEW-YORK MICROSCOPICAL SOCIETY 



Vol. X. JULY, 1894. No. 3. 



A CONTRIBUTION TO THE HISTORY OF THE 

 FORMATION OF THE LICHEN THALLUS. 



BY CARLTON C. CURTIS. 

 (Jiead March i6ih^ 1894.) 



About five months ago some material was brought into our 

 laboratory that proved to be an exceedingly early stage in the 

 development of the lichen thallus. The observations on, and il- 

 lustrations of, this condition and subsequent development that 

 have extended down to the time of writing are here presented, not 

 as any considerable addition to the subject of lichenology, but 

 because the study awakened much interest among the students, 

 and some points were made clearer than could be gathered from 

 the literature of the subject, and, as far as known, there are no 



Explanation of Plate 44. 



Fig. 1.— Filament of the fungus attacking an algal cell. 



Fig. 2. — The subsequent development of the form shown in Fig. 1. The algal cell has 

 divided several times, and the hyphae have extended themselves to form a bushy 

 cluster. 



Fig. 3.— a still older growth. The clusters are becoming covered above and below 

 •with a mass of filaments. 



Fig. 4.— a longitudinal section through the young thallus. a, Upper medulla; 6, 

 gonidial or algal zone; c, lower medulla; d, rhizoids. 



Fig. 5.— a longitudinal section through a sporocarp. a, The dense tissue of the stipe 

 — the lines are not intended to represent the structure; 6, the gonidia largely confined 

 to the periphery of the sporophore; c, hymenium— the dotted portion representing the 

 paraphyses projecting beyond the asci. 



Fig. 6.— a longitudinal section of the apothecium. a, Paraphyses; 6, ascus with 

 spores; c, hypothecium— the hyphae anastomose more than is indicated; d, a small 

 gonidial group. 



