376 abstracts: mycoi^ogy 



rivers flow through marked glacial troughs; in the upland through 

 wide valleys; and in the costal plain nearly at the surface of the tundra. 

 Canning River is 120 miles long; other large streams of the area are the 

 Okpilak, Hulahula, and Sadlerochit. 



Under Geology are described: Paleozoic, Mesozoic and Cenozoic 

 rocks. Pleistocene glaciers extended from the mountains well down the 

 valleys but did not reach the coast. Present glaciers are confined to the 

 higher mountain valleys. 



The occurrence of ground ice is described and the literature of this 

 subject reviewed in considerable detail. The author concludes that the 

 two varieties of ground ice most common in northern Alaska are formed 

 by the burial of river ice by sediments, and the growth in place of ver- 

 tical ice wedges. J. T. Pardee. 



MYCOIvOGY. — Further data on the susceptibility of rutaceous plants 

 to citrus -canker. H. Atherton Lee. Journ. Agr. Res. 15: 

 661-665. 1918. 



Inoculation tests made in the Philippine Islands with Pseudcnninas 

 citri upon 24 species representing 20 genera of the family Rutaceae, show 

 that 19 of the species are susceptible in greater or less degree. It thus 

 appears that citrus-canker is not closely limited to the genus Citrus, 

 but has a wide range of hosts among the Rutaceae. 



Severinia buxifolia, Aegle marnielos, and Balsamocitrus gabonensis 

 all close relatives of Citrus, may safely be called immune to citrus 

 canker. Xanthoxylum rhetsa and Triphasia trifolia seem to be immune. 



Chalcas (Murraya) exotica, Atalantia disticha, and Fortunella (Citrus) 

 japonica, also closely related to the genus Citrus, are strongly resistant 

 to citrus-canker. 



Claucena lansium, Feronia limonia, Feroniella lucida, Chaetospermum 

 glutinosum, Hesperethusa crenulata, Paramignya longipedunculata, Cit- 

 Topsis schweinfurthii, Atlantia citrioides, Eremocitrus glauca, Fortunella 

 hindsii, Microcitrus australis, M. australasica, Toddalia asiatica, Evodia 

 ridleyei, E. latifolia, and Melicope triphylla, of different relationships to 

 the genus Citrus, all produce positive results when inoculated with 

 Pseudonionas citri, at needle punctures. Of these, Claucena lansium 

 and Feronia limonia develop infection very slowly, the others fairly 

 quickly. 



Chaetospermum glutinosa shows naturally occurring infections of 

 citrus-canker and in the Phihppines its susceptibility is easily greater 

 than that of the sweet orange {Citrus sinensis). Fortunella hindsii 



