RUST FUNGI 199 



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

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

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

 peridiimi, hence, a caeoma and the urediniospores appear in long chains 

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

 by the peridiimi, 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 

 excdsa, in Europe, and on P. rubra in this country. The aecia of Cronar- 

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

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

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

 united into cylindric colimms, which are homy when dry. The 

 European C. ascUpiadtum has its secia on the branches oiPinus sUvestris 

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

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

 C. quercuum has its aecia on Pinus and its urediniospores and teliospor^ 

 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 secium 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. rvbrum. The fungi of the genus ildampsora are mostly heteroecious. 

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

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

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

 tremuloides and P. balsamifera. Calyptospora 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 mtis-idaa, 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 F. pemisyhanicum 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 



