I05 



to wounds in plant cells." Dr. Nichols found that the coarser 

 algae lend themselves admirably to this investigation, the plants 

 being mounted in water and punctured freehand with a steel 

 needle. In Chaetomorpha mela^onium f. lypica, after the punc- 

 ture of a cell, a clear liquid comes out and passes into the water. 

 Within a second or two starch grains, etc. begin to accumulate 

 at the opening, forming a plug, which turns dark in a few minutes 

 and apparently hardens, closing the opening. In two minutes 

 all movements from the cell into the water has usually ceased. 

 By plasmolyzing, it can be demonstrated that in about 45 

 minutes a new membrane has started to form underneath the 

 base of the plug. In i}4 hours the membrane is completely 

 formed and a new cell wall is gradually deposited. The plug 

 gradually becomes transparent and in a month has disappeared. 



In Nitella the circulation of the protoplasm with its plastids, 

 makes the results easy to follow. A certain number of plastids, 

 loosened by the needle, rush out into the water, but the other 

 cell contents do not diffuse as in Chaetomorpha. The membrane 

 is formed apparently as in Chaetomorpha. Rotation of the 

 protoplasm, which may cease immediately at the time of punc- 

 turing, it resumed simultaneously very soon after, throughout 

 the internode, with the exception of an area near the wound. 

 The renewed movement increases until the normal rate — 1.5-2 

 seconds per 80 [i — is reached. A mass collects about the wound, 

 which interferes with the movement here, but otherwise the 

 movement is normal 24 hours after wounding. On repuncturing 

 in the same cell after a short interval, 1-2 minutes, the same 

 process is repeated, but the time necessary for the normal move- 

 ment to be regained is longer. When punctures are frequent 

 but after a longer interval, 10-15 minutes, recovery is more and 

 more rapid, possibly because the available plastids are fewer and 

 so do not hold the wounds open. One internode was punctured 

 87 times and its final death may not have been from this cause. 

 A new cell wall is formed just as in Chaetomorpha. 



Other subjects employed in the experiments were Vaucheria; 

 Spirogyra, which, although used successfully, was difficult to 

 puncture; Chara, the cortical cells of which never healed, although 

 the internodal cells did; Elodea, the leaf cells of which, although 

 forming a plug, invariably died after 24 hours; Bryum, in which 

 not even a plug is formed; and cells of fern prothallia and An- 



