02 Newc()ml)e, Thigmotropisni of terrestrial rnots. 



employed were siiitalile and tlie niimber of plants .suf fielen t to 

 Warrant tlie conclusions drawn. 



B. Experimenta] Part. 



1. Testing the Sensitiveness of tlie (xrowiiig Toiiit. 



1. Preparations in damp-cliambers. 



The damp-chambers used in the foUowing experiments were 

 niade of glass jars whose sides were lined with filter-jjaper dip- 

 ping into water in the bottom of the jar. The seedlings were 

 nsually suspended on bars of white pine, strips of cloth hekl by 

 rubber bands securing the upper part of the root against blot- 

 ting paper covering the wooden bar. In many instances the 

 evaporating surface in the Chambers was greatly increased by 

 stretching several sheets of absorbent paper over wire-frames 

 extending froni the bottom to the top of the Chamber. When 

 such delicate seedhngs as those of Brassica alba Boiss. and 

 Fagopyrmn esculentum Moench were used, resort was had to a 

 little damp-chamber for each seedling. To prepare the last- 

 named device, wide-mouth glass bottles with a capacity of 50 cc 

 were lined with filter-paper; a flat cork one or two millimeters 

 narrower than the mouth of the bottle was perforated in the 

 middle; 2 pieces of wire were fastened in the cork and beut so 

 as to hook over the mouth of the bottle, and thus suspend the 

 cork in the lower part of the neck of the bottle. A little water 

 in the bottom of each bottle made it a good damp-chamber. 

 The seedlings, nsually 24 hours l^efore using, were fastened in 

 the central Perforation in the cork by means of a little wet 

 cotton. These small bottles finally were placed in a large glass 

 jar, itself a damp-chamber. V>y the foregoing device, when one 

 of the seedlings was taken out to attach an object to its root, 

 none of the others was endangered by exposure to the dry 

 atmosphere. 



A few incidental experiments have already been made by 

 various authors by attaching so-called inert bodies to the side 

 of the root-tip. Wiesner i) obtained no curves when he attach- 

 ed bits of wood and grains of sand to the root-tip. Detlef- 

 sen^) obtained negative curves in several roots when he laid on 

 one side of the tip a scale of glass so thin that it would apply 

 itself to the curving surface of the root. When he used rigid 

 bits of glass, no curves resulted. After the flexible glass had 

 been on the root for 2 days the cells beneath were dead. To- 

 maschek^ and Burgerstein*) found that a bit of wet clay 



1) Wiesner, Das Beweguiigsvermögen der Pflanzen. Wien 1881. 143. 



2) Detlefsen, Über die von Darwin ])eliatij)tete Gehirnfanktion der 

 Wuj-zeln. (Arbeit, d. bot. Inst. Würzbnrg. II. 639.) 



3) Tomas eh. ek, Zu Darwins „Bewegungsvermögen der Pflanzen". 

 (Review in Bot. Centralbl. XIII. 185.) 



4) Burgerstein, Einige Bemerkungen zur Darwin'schen Wurzelkrüm- 

 mung. (Review in Bot. Centralbl. XIII." 185.) 



