258 INFLUENCE OF CORRELATION AND EXTERNAL STIMULI 



by the fructifications of many fungi is no doubt connected with distribution 

 of spores also. These heliotropic movements influence, in some cases, 

 the form of the fructification. 



It is possible by changing the direction of the influence of light to 

 cause the neck of Sordaria fimiseda 1 to assume any position desired, 

 even to give it a spiral twist, because it turns itself always to the light ; 

 the fructifications of Ascobolus and Peziza likewise turn themselves to the 

 light, so that their disk receives the rays at a right angle. 



The colour and consistence of the fructifications of many Sphaeri- 

 aceae' 2 , as well as the length which their neck below its opening reaches, are 

 dependent upon light. In Sphaeria velata, for example, the neck normally 

 attains a length of i mm., but if light be excluded it may reach as much 

 as 5 mm. This is not the place to discuss the heliotropic phenomena 

 of Fungi, but it is of interest for us to note that in many the formation of 

 the sporophore depends on light, whilst the mycelium is not influenced 

 by light 3 . Thus in Pilobolus microsporus the formation of sporangia is 

 suppressed in darkness, whilst their stalks are laid down but are puny and 

 slender. The influence of light for a few hours suffices to bring about the 



o o 



changes which lead to the formation of sporangia. Sphaerobolus stellatus 

 also remains completely sterile in the dark. Many Hymenomycetes lay 

 down their fructifications in darkness, but these grow abnormal. Schroter 

 found the sporophore of Stereum sanguinolentum in coal mines had 

 only seldom the form of spread-out plates or half caps, which is the 

 normal one ; the whole sporophore was usually broken up into a great 

 number of coral-like spreading branches, forming broad ridges and 

 spikes hanging from the props. Many species of Lentinus also under 

 such conditions form, instead of the 'stalked ' pileus, white cylindric strands 

 which remain either simple or make coral-like branchings. If such 

 branches reach the light, they commonly produce at the apex reduced 

 or more or less normal pilei. Here then the influence of the light 

 favours the formation of the pileus ; it does not affect the first prim- 

 ordia of the fructification. Similarly in some species of Coprinus, for 

 instance, C. stercorarius, C. plicatilis, C. ephemerus, isolated primordia of 

 fructifications appear in the dark, but they do not unfold normally, the cap 

 is arrested while the stipe is abnormally elongated ; in light, on the other 

 hand, the fructifications are very freely laid down almost to the complete 



1 Woronin in De Bary and Woronin, Beitr. zur Morphologic nnd Physiologic der Pilze, iii. p. 10. 



2 St. Schulzer v. Miiggenburg, Des Allbelebenden Lichtes Einfluss auf die Pilzwelt, in Flora, 

 1878, p. 118. Older observations, including those of Fries, are cited by Elfving, Studien liber die 

 Einwirkung des Lichtes auf Pilze, Helsingfors, 1890. 



3 See Brefeld, Untersuchungen aus dem Gesammtgebiete der Mykologie, iii. pp. 87, 114, 115; 

 viii. p. 275 ; also Schroter, Uber das Wachstum der Pilze im Dnnkeln, in Jahresber. der Schlesisch. 

 Gesellsch., 1884, p. 290. 



