256 



RESEARCHES ON FUNGI 



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n\ 



Fig. 123. — Diagram illustrating variations in helio- 

 tropic curvature in tlie asci of different species 

 of Discomycetes. The arrows indicate the 

 direction in which the asci were illuminated 

 during their development. All the asCi, at first, 

 were straight, and their appearance (including 

 an indication of the position of origin of the 

 rudiment of each operculum), just before they 

 began to bend, is indicated in part by brokeii 

 lines. Heliotropic curvature toward the source 

 of liglit began : in A (as in Aleuria vesiculosa) 

 when the ascus was only half -grown in length ; 

 in B (as in Ciliaria scutelhttd) when the ascus 

 was about five-sixths grown in lengtli ; and 

 in C (as in Sarcoscypha protrnctn) when the 

 ascus was almost full-grown in length. The 

 cvirvature of the central broken line which 

 represents the morphological axis of each ascus 

 indicates that even in C, which externally has 

 the appearance of a straight cylinder, the lateral 

 position of the operculum has been attained, as 

 in A and B, by a heliotropic curvature. 



1 In litt., 1927 and 1928. 



/ of the ascus, which he 

 calls the ascostome, in a 

 number of tropical Dis- 

 comycetes, e.g. species of 

 Phillipsia and Cookeina, 

 is a purely ''morpho- 

 logical character " not 

 influenced by the ex- 

 ternal stimulus of light, 

 but he admits ^ that he 

 has not observed the 

 fruit-bodies in the living 

 condition and has no ex- 

 perimental basis for his 

 assumption. In view of 

 my own investigations 

 on the obliquely situated 

 ascostomata of Sarco- 

 scypha protracta which 

 always look toward the 

 strongest incident rays 

 of light, supported by 

 other investigations on 

 the position of the asco- 

 stomata of the asci of the 

 discoid fruit-bodies of 

 Ciliaria scutellata, etc., 

 recorded in the next 

 Chapter, I am unable to 

 accept Seaver's assump- 

 tion. It is my opinion 

 that the internal tend- 

 ency of every ascus is to 

 produce itsascostomain 

 a radially symmetrical 

 position at the ascus 



