572 COMPARATIVE MORPHOLOGY OF FUNGI 



in the spring and germinate immediately with an apical basidium which 

 ruptures the wall of the host cell and produces its spores outside the 

 epidermis. In Milesina they develop on overwintered fronds and ger- 

 minate at once. 



While in Melampsorella and Milesina the zeugites, because they are 

 not encysted, should not be designated as teliospores in the true sense 

 of the word, in Thekopsora, Pucciniastrum and Melampsora they have a 

 firm membrane and become hypnospores. Besides, they do not arise 

 individually scattered over the host tissue but are collected in more definite 

 sori as true telia. In Thekopsora, they occur in the epidermal cells, 

 usually several in one cell, almost completely filling it and by mutual 

 pressure adhering in a plate (Fig. 383, 2). They divide by vertical or 

 somewhat oblique walls into two to four daughter cells, each of which 

 sends out a basidium. Pucciniastrum behaves similarly, its telia instead 

 of being intracellular are intercellular under the epidermis. In Melamp- 

 sora (Fig. 383, 3) the teliospores are joined laterally into a hypodermal 

 or subcuticular crust; in them, however, the longitudinal division into 

 daughter cells is absent. 



Faull (1928) summarizes developmental tendencies within the 

 family as follows : Uredinopsis, Milesina and Hyalopsora are restricted to 

 Abies and ferns, while the others are found on Abies, Larix or Picea and 

 angiosperms, although in the latter case none are known on recent families 

 such as Orchidaceae and Compositae. The characteristic yellow pigment 

 of rusts is lacking in Uredinopsis and Milesina, being present in the other 

 genera. The pycnia are comparatively large and deep seated in Uredinop- 

 sis, Milesina and Hyalopsora and small and superficial in the others, 

 becoming quite abortive in Calyptospora. The uredinium is quite con- 

 stant but absent in Calyptospora. It is the largest in Uredinopsis, its 

 peridium being simple in Uredinopsis, Milesina, Hyalopsora and Melamp- 

 sorella and showing specialization in Pucciniastrum, Thekopsora and 

 Melampsoridium. The telia are diffuse especially in Uredinopsis, less 

 so in Milesina, Hyalopsora and Melampsorella, tending to become com- 

 pact in Pucciniastrum, Thecopsora, Melampsoridium and Calyptospora. 

 They are subepidermal in Uredinopsis, Pucciniastrum and Melampsori- 

 dium, intraepidermal in the other genera; they are occasionally sub- 

 epidermal in Milesina. The teliospores are irregular in form and number 

 in Milesina and Hyalopsora. 



Cronartiaceae. — Here the teliospores are morphologically at approxi- 

 mately the same stage of development as the Melampsoraceae. Several 

 spores are cut off catenulately on the hypha, and the whole spore mass of 

 the sorus clings together into a columnar spore body. In Cronartium 

 ribicola the telia so extensively agree with the earlier described uredinia 

 in the young stages, e.g., in the formation of the hyphal knot, peridium 

 and sporiferous basal cells, that in this stage it is not possible to dis- 



