HELIOTROPISM OF ASCI IN DISCOMYCETES 313 



which are sterile exter- 

 nally (Figs. 152 and 153). 

 The fruit-body of the Mor- 

 chellaceae, owing to its 

 possessing a subdivided 

 hymenium, is said to be 

 compound.^ 



The alveoli on the 

 exterior of the pilei of the 

 Morchellaceae, as defined by 

 their exterior sterile ribs, 

 may be irregularly rounded, 

 irregularly polygonal, or 

 more or less longitudin- 

 ally elongated. When the 

 alveoli are rounded or 

 polygonal or but slightly 

 elongated, they remain 

 simple, although their in- 

 ternal lateral walls are 

 usually plicate (Fig. 152). 

 On the other hand, when 

 the alveoli are much 

 elongated longitudinally 

 (Figs. 154 and 155), they 

 are usually broken up by 

 more or less well developed 

 transverse hymenium- 

 covered ridges. Thus a 

 much elongated primary 

 alveolus may be subdivided 

 into secondary alveoli . 

 Each species has alveoli 

 of characteristic shape. 

 Thus the alveoli are : in 



Fig. 154. — A fruit-body of Morchella deliciosa. 

 The pits (alveoli) are much elongated and 

 are divided transversely into secondary 

 alveoli. Collected at Ottawa by W. S. 

 Odeil. Photographed by the Photographic 

 Division of the Geological Survey of Canada. 

 Natural size. 



^ E. Boudier, Histoire el Classification des Discomycetes d'' Europe, Paris, 1907, p. 30. 



