igS MYCOLOGY 



formation of the ascus, the two nOn-sister n-uclci fuse after which the 

 fusion nucleus divides, the first division being heterotypic (meiotic, 

 reducing, possessing synapsis and diakinesis stages), and the two fol- 

 lowing ones, which result in the formation of eight ascospores, are 

 homotypic. From this point of view, the ascus is a spore mother cell 

 comparable to the tehospore of the rust fungi, but forming an octad, 

 not a tetrad of spores. The probable phylogeny and relationship of 

 the UredinEjE to the other groups has been set forth in a family tree 

 by Grove. 



Arthur, who has studied the rusts carefully for many years, pro- 

 posed at the International Congress of Botanists held in Vienna in 

 1905 an arrangement of the families, genera and species of the rusts, 

 which differs materially from the older classifications. 



As this classification of Arthurs has not been elaborated in detail, 

 it has been considered best to follow the arrangement of families, sub- 

 families and genera given in Engler and Gilg's "Syllabus der Pflanzen- 

 familien" (7th Edition, 1912) as following the conservative and 

 older treatment. 



Family Endophyllace.e. — The teliospores are abstricted suc- 

 cessively in long rows and are surrounded by a peridium which is 

 formed like that of a typic aecidium of Puccinia from the peripheral 

 cell rows, but is sometimes less strongly developed. These teUospores 

 are perhaps more correctly called aecio-teliospores, as they are separated 

 from each other by intercalary cells hke true a;ciospores and arise 

 from a fusion cell, but they germinate by the formation of a basidium 

 and basidiospores like true teliospores. The germ pores are impercep- 

 tible and the spore wall is colored. Pycnia are present and both kinds 

 of sori are subepidermal. 



Endophylhim sempervivi lives parasitically on the house leek, Sem- 

 pervivum tedorum, and several other species of Sempervivum in Europe 

 from April to August. It has been proved by de Bary, Hoffmann and 

 others, that the basidiospores produced by the aecio-teUospores infect 

 the leaves of the house leek and from them arises a myceUum which 

 lives over the winter in the stem. The following spring, it forms 

 pycnia and ascio-teliospores and the affected leaves are more erect 

 than normal ones, twice as long, narrower and yellowish at the base. 

 Family Melampsorace^.— The teliospores are unstalked, one- to 

 four-celled, but placed singly on dilated hypha; in the tissues of the 



