392 NATURAL SCIENCE [June 



roots of various earth-inhabiting plants might be induced to pene- 

 trate living vegetable tissues. Peirce, in examining the matter, 

 took potato-tubers and split them in half. In small slits on the 

 one half he inserted seeds of Brassica naims or Sinapis alba, and 

 then tightly bound the two parts of the tuber together again. He 

 left these manipulated potatoes for twelve days in moist sawdust 

 and then unbound them. He found that nearly all the seeds had 

 germinated, and that whilst a few had grown along the line of the 

 cut in the tuber, others had penetrated the substance of the 

 potato. In some cases growth had been so vigorous, that not only 

 had the parenchyma of the half-tuber been penetrated, but the 

 root had actually made its way through the cork-layer on the 

 outside and grown into the sawdust. Other experiments, rather 

 differently arranged, showed that Pisnm and Vicia Faha could 

 likewise penetrate living tissues. Not only did the roots of these 

 plants grow into tubers of potato but also into the stem of 

 Impatiens sultani, leaves of Echivaria, Aloe and other plants. One 

 of the most interesting and significant results which Peirce ob- 

 tained was to grow specimens of Pisum as parasites upon other 

 plants from the seedling stage until flowering. Impatiens sultani 

 formed the most satisfactory host. In Pis?M7i-plants grown under 

 these peculiar conditions the root-system was formed in a fairly 

 normal manner, although the rootlets were destitute of hairs ; the 

 stem, however, was stunted, but bore leaves and a few flowers. 

 The importance of this experiment to the student of parasitism will 

 at once be evident. Eudolf Beer. 



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