402 CLASS BASIDIOMYCETEAE- 



to a promycelium. The teliospores are produced under the epidermis or in 

 the epidermal cells or in the mesophyll, or very rarely (Cystospora, Go- 

 plana) the basal cells from which they arise may push out through a stoma 

 so that the teliospores are then produced externally. The stalked types of 

 teliospores are formed subepidermally and become external by the rupture 

 of the epidermis. In some genera they are formed in separable chains and 

 the telium is surrounded by a peridium which bursts the epidermis and 

 opens to allow the teliospores to escape. In the fern rusts of the genus 

 Uredinopsis the teliospores are produced in the mesophyll of the leaf 

 singly or united, two, three, or four together, into a compound teliospore, 

 each of whose component cells gives rise to a separate promycelium which 

 emerges from the leaf surface. In some species of Pucciniastrum the telio- 

 spores are produced in groups of two to four cells in the epidermal cells of 

 the host, but in other species these clusters of teliospores may be aggre- 

 gated laterally into a subepidermal crust. In Cronartium the teliospores 

 are joined laterally and longitudinally into a tall waxy column which 

 pushes out through the epidermis to a length of up to 6 or 8 mm. In 

 Melampsora and Coleosporium the teliospores are crowded laterally into a 

 subepidermal or subcuticular crust. Among the stalked forms Uromyces 

 has but a single teliospore at the apex of its stalk, Puccinia has two united 

 teliospores on the single stalk, in Phragmidium one stalk bears a row of 

 three to eight or more teliospores. In Pucciniosira the telium has a perid- 

 ium and the teliospores are formed on a stalk in chains which break apart 

 into units of two teliospores each. In Ravenelia the stalk bears a head of 

 laterally united teliospores, below which hang colorless cells, the so-called 

 "cysts." Usually in systematic literature these various types of compound 

 teliospores are spoken of as single teliospores although properly each cell 

 from which a promycelium arises is a teliospore. 



The order has been divided into many families or into two families. 

 The author follows Dietel (1928) and the later works of Arthur (1929, 

 1934), both of whom recognize but two families, each divided into several 

 tribes. 



Family Melampsoraceae. Teliospores without stalks, produced 

 singly or united in groups of two to four in the mesophyll or just below or 

 within the epidermal cells, or united laterally into subepidermal or sub- 

 cuticular crusts, or united into separate vertical chains or into chains 

 which are united laterally into a waxy column which bursts through the 

 epidermis. Aecia mostly on species of Family Pinaceae. There are 15 to 20 

 genera and about 300 species. This family clearly includes the most primi- 

 tive living representatives of the order. The genus Uredinopsis with its 

 colorless thin-walled teliospores, single or united by twos, threes, or fours, 

 in the mesophyll of the leaves of ferns, its two kinds of colorless uredio- 

 spores, thick-walled and thin-walled, the sori surrounded by peridia, and 



