Shear and Dodge : Patellina, Leptothyrium, Peziza 147 



II. Pycnidial Stage, Sclerotiopsis concava (Desm.) n. comb. 



The pycnidial form has been most frequently referred to Lep- 

 tothyrium macrothecium Fckl. A study of the type of the genus 

 L. lunariae Kze., however, shows that this species is not congeneric 

 with it. In further search for a generic name it was found that 

 the genus Sclerotiopsis of Spegazzini was based on the same 

 species as ours. His type S. australasica proves indistinguishable 

 from Leptothyrium macrothecium. Sclerotiopsis is the oldest un- 

 questionable generic name we have found for the pycnidial form. 

 The pycnidium is a large, closed, shield-shaped or depressed, puk 

 vinate body which is packed with an enormous number of spores. 

 Like the sporodochial stage this fruit body arises intra-epider- 

 mally so that as growth continues the cuticle together with the 

 upper wall of the epidermal cells is stretched and pushed up 

 until a shield-shaped or pulvinate body is formed, ' entirely cov- 

 ered by the upper part of the epidermal layer. On dewberry 

 canes the epidermis may split at the center or in a line along the 

 center. On leaves and large stems these pycnidia are nearly cir- 

 cular in outline often collapsing at the center on drying. This is 

 the condition which suggested the specific name " concava " to 

 Desmazieres. 



The color varies with the age of the pycnidium, being at first 

 gray to argillaceous, then light brown. Mature specimens are 

 shining chestnut brown or almost black. These changes of color 

 are well shown on leaves of Epilobium. As carbonization of the 

 cell walls progresses the color approaches more nearly chestnut 

 brown. On a substratum such as the blackberry cane the pycnid- 

 ium is very smooth and shining, a feature not noticeable where 

 the epidermis, such as that of a young Oenothera or Quercus leaf, 

 is rough or covered with fine hairs. The pycnidium, being intra- 

 epidermal, is long covered by the cuticle and cuticularized layer of 

 the epidermis (pi. o, fig. 17). The outer wall of the pycnidium is 

 composed of small polyhedral thick- walled brown cells, the outer 

 ones being somewhat flattened and brick-shaped. The inner 

 ones have much thinner walls and are more angular, forming a 

 rather broken or jagged border line. The basal or lower wall is 

 made up of at least three distinct tissues. The first lying next to 



