4 University of California Publications in Botany [Vol. 6 



also been collected at various localities on the western coast of North 

 America by Dr. N. L. Gardner. The greater amonnt of the material, 

 however, has been collected at San Pedro and Santa Monica on the 

 coast of Southern California by Dr. Gardner and has occurred on 

 Laurencia suhopposita (J. Ag.) {CJiondria suhopposita J. Ag.. 1892. 

 p. 149), Chondria nidifica Harv., and Ch. atropurpurea Harv. The 

 material, thus gathered together, has been subjected to critical exami- 

 nation, particularly by Miss Mabel E. Brown in 1911 and by John E. 

 Guernsey in 1913. The notes and drawings of these graduate students 

 in the University of California have been available and have been of 

 the utmost assistance in the preparation of the following account. 



IV. HOST PLANTS 



From what has been said above it will be noticed that all the 

 specimens of Janczeivshia thus far noted by others or mentioned by 

 the writer have been found upon members of the Rhodomelaceae. the 

 same family to which Janczewskia itself belongs. Further than this, 

 the hosts are species of Laurencia, CJiondria, and Cladhymenia, mem- 

 bers of two subfamilies of the Rhodomelaceae, viz., the Laurencieae 

 and the Chondrieae, while the genus Janczewskia itself is clearly 

 closely related to Laurencia and is a member of the Laurencieae. 

 Among the hosts are four or five species of Tjaurencia: L. ohtusa of 

 southern Europe, L. Forsteri of Tasmania and Australia, L. suhop- 

 posita and L. pinnatifida of the western coast of North America, and 

 an unidentified species in South Africa. Two species of Chondria are 

 found among the hosts of Janczewskia, Ch. nidifica, and what passes 

 at present for Ch. atropurpurea, both on the southern coast of Cali- 

 fornia. The last of the possible eight hosts is Cladhymenia ohlongi- 

 folia of New Zealand. So far as the studies of others thus far pub- 

 lished and our own as reported below tend to show, there is evidence 

 that each host plant is infested with its own peculiar species of 

 Janczewskia. This seems certain for six of the eight hosts, where the 

 material has been sufficiently ample for detailed study and compar- 

 ison. It is probable that careful search and study will reveal still 

 other species of Janczewskia on other Chondrieae and Laurencieae. 

 It certainly affords material for careful consideration to discover that 

 Janczewskia, a laurencioid genus of several species at least, is con 

 fined in its parasitism to laurencioid and closely related chondrioid 

 hosts. 



