RUST FUNGI 199 



host, or arranged side by side in flat crusts. Germination of the teHo- 

 spore results in the formation of a four-celled basidium, each cell of 

 which forms a single basidiospore. The secium is typically without a 

 peridium, hence, a cseoma and the urediniospores appear in long chains 

 without a peridium, or arising singly, and then mostly surrounded 

 by the peridium, or mixed with paraphyses. 



The genus Melampsoropsis includes fungi whose teliospores are in 

 cushion-like layers, which break through the epidermis of the host. 

 M. ledi has its teliospores on Ledum and its aecia on the spruce, Picea 

 excelsa, in Europe, and on P. rubra in this country. The secia of Cronar- 

 tium have a broad, inflated irregularly torn peridium. The uredinium 

 is enclosed in a hemispheric peridium, which opens at the summit by a 

 narrow pore. Its teliospores are abstricted in long chains and remain 

 united into cylindric columns, which are horny when dry. The 

 European C. asclepiadeum has its gecia on the branches of Plnus sihestris 

 in May and June, and its urediniospores and teliospores on PcBonia 

 officinalis in gardens, as also on Vincetoxicum, Cynanchum and Verbena. 

 C. quercmim has its aecia on Pin us and its urediniospores and teliospores 

 on at least twenty species of oak in North America. C. ribicola is a 

 dangerous parasite called the white pine blister rust and against it the 

 United States Government has an active quarantine. Its aecium is con- 

 fined to the five-leaved pines, one of which is Pinus strobus, our eastern 

 white pine. These are found in the months from March to June. The 

 urediniospores and teliospores grow on the currants, Ribes nigrum and 

 R. rubrum. The fungi of the genus Melampsora are mostly heteroecious. 

 There are seven species recorded for North America. Of these Melam- 

 psora meduscB causes the poplar rust. The aecium occurs on the larch, 

 Larix, and its urediniospores and teliospores on Populus deltoides, P. 

 tremuloides and P. balsamifera. Calypfospora is a genus of rusts, the 

 life history of which has been investigated by Hartig, Kuhn and 

 Bubak. In July to September, the teliospores appear on the stems of 

 Vaccinium vitis-idcBa, where the stem becomes swollen and elongated 

 and at first of a pink color passing to brown. It occurs on other species 

 of Vaccinium, including V. pennsylvanicum in the United States. The 

 aecia are found in Europe on leaves of Abies pectinata and in America 

 on A . balsamea. 



Family Coleosporiace^. — The aecium in this family has a perid- 

 ium. The flattish, linear pycnia are subepidermal dehiscing by a 



