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collector are given in Table 1, The plant species are listed alphabetically. 

 If more than one collection vras made for a species these collections are 

 arranged (a) geographically by provinces from west to east and (b) vrithin 

 each province by date of collection from early season to late. Periodic 

 collections of Apocynum and Asclepias, urtiich were made in the same localities, 

 are grouped together in the table and the collection localities are deleted 

 for all but the first sample. Accession numbers are included with the lo- 

 cality for the material that ii«as established in plots at Ottawa. 



The great majority of plants analyzed had benzene extracts of less than 

 one percent, indicating that th^ contained little or no rubber. Among the 

 species with more than two percent were Apocynum androsaemifoHiim 2 ,1%, 

 Asclepias ayriaca 2.5/S, A. sullivantii 2.1^, Euonymus europaea 3*2%, E. maac- 

 kii 6.1^, and E. yedoensis 2,7/S. In addition species of the following genera 

 had benzene extracts between one and two percent: Apocynum, Asclepias, Eucom- 

 mia, Euonymus, Euphorbia, Lonicera, Parthenium, Solidago. and Tanacetum . 



Rubber apparently is not stored uniformly in the roots and shoots of all 

 plants. In species of Apocynum, Asclepias, Lonicera , and Solidago the leaves 

 had higher benzene extracts than did the stems or roots. In species of Euony- 

 mus, however, the highest benzene extract was in the bark, while in Euphorbia 

 corollata it was in the roots, and in Parthenium argentatum it was in the stems. 



Analyses of the periodic collections from the same locality of Apocynum 

 androsaemifolium and Asclepias syriaca indicate that the rubber content of the 

 leaves increased with the advancing season. 



Large acetone extracts were obtained from sane of the samples^ for exam- 

 ple Lonicera tatarica U7%i Rhus typhina k5%t R. glabra 35%, Lor;icera ruprech- 

 tiana 39^> L. amoena 35%t Euonymus .japonica 3k%f Apocynum androsaemifolium 33^, 

 and Betula papyri f era 30^. In addition species of the genera Acer, Arctosta- 



