Reprinted for private circulation from 

 THE BOTANICAL GAZETTE, Vol. LXVI, No. 3, September 1918 



SECONDARY PARASITISM IN PHORADENDRON 



BROWN S illustration of Phoradendron californicum parasitic on 

 P. flavescens 2 has a twofold interest. First, it records a case of secondary 

 parasitism which seems to be very rare indeed. It has never, so far as 

 I am aware, been noted by workers at the Desert Botanical Laboratory, 

 a number of whom have been especially interested in parasitism. For 

 the most part P. macrophyllum and P. californicum occur on quite 

 different hosts. 3 Second, the case is of interest physiologically, as 

 BROWN suggests, in its relation to osmotic and other physical phenomena. 

 HARRIS and LAWRENCE, in their study of the sap properties of Jamaican 

 montane rain forest Loranthaceae, 4 find that in these forms the sap 

 extracted from the green stems of the leafless species shows lower osmotic 

 concentration than that from the foliar tissues of the leafy forms. Thus 

 in working with 7 species of Loranthaceae they found average values 

 of the freezing point lowering of 1.153, I - I 7^, and 1.177 in the 

 leafless species as compared with i .305, i .347, i .400, and 1.650 in 



1 BROWN, J. G., Mistletoe vs. mistletoe. Box. GAZ. 65:193. jig. /. 1918. 



2 This is presumably P. macrophyllum Cockerell, the P. flavescens macrophyllum 

 of ENGLEMANN and of some subsequent workers, or one of its varieties. The host 

 here, as Professor BROWN has kindly written me, was a Fraxinus. 



3 TRELEASE (The genus Phoradendron, p. 14, Urbana. 1916) notes that P. cali 

 fornicum, while occurring exclusively on angiosperms, belongs to a group, the &quot;Pauci- 

 florae,&quot; which with this and one other exception is limited to coniferous hosts. 



4 HARRIS, J. ARTHUR, and LAWRENCE, J. V., On the osmotic pressure of the 

 tissue fluids of Jamaican Loranthaceae parasitic on various hosts. Amer. Jour. 

 Bot. 3:438-455. 1916. 



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