90 Forest Club Annual 



absent. Many species of the rusts, are hetercecious, among which 

 are some of the most destructive diseases known. 



Aecidium 



In this genus the peridium enclosing the aeciospores is cup- 

 shaped or urn-shaped, rarely cylindrical, the margin often crenate 

 or laciniate and revolute. The aeciospores are globose or angu- 

 lar, continuous, smooth or verrucose, orange-yellow, produced 

 in chains. 



Aecidium fraxini Schwein. 



Pycnia numerous, scarcely elevated above the upper surface 

 of the leaf. Aecia usually very abundant, elongate, cylindrical, 

 finally lacerate with the subdivisions reflexed. Aeciospores el- 

 liptical or globose, episporium thin, rough, 24-32 x 21-24 microns. 

 This species is sometimes very abundant on the leaves of Fraxi- 

 nus lanceolata, causing distortion and curling both in the blades 

 and petioles. 



Melampsora 



Teliospores dark, unicellular; sori arising from dark spots 

 which burst through the epidermis. The yellow urediniospores, 

 with an episporium beset with fine prickles, break through the 

 epidermis in more or less orbicular spots or sori, and are very 

 conspicuous during late summer. 



Melampsora populina (Jacq.) Lev. 



Uredosori roundish, at length reddish-yellow, often con- 

 fluent. Urediniospores elliptical or ovoid 28-38 x 15-20 microns. 

 Teliosori on the upper side of the leaf, often confluent, at first 

 reddish-brown, finally dark brown. The urediniospores are usu- 

 ally accompanied by paraphyses. Very common during July and 

 August on Populus deltoides and other poplars. 



Melampsora salicina Lev. 



This is a collective name since there are now several species 

 recognized within the old species. The various forms occur upon 

 species of Salix, such as 5*. alba, S. cor data, S. longifolia, S. 

 nigra, etc. 



FUNGI IMPERFECTI 



Sphaeropsidales. 



In this order the conidia are borne on simple or branched 

 threads, so-called basidia, in a perithecium-like fruit called a 

 pycniclium. The pycnidia are globose, conic, elongate, dimidiate, 



