( 193 ) 



;is PiNOT wlio used llicin oiilj about oiio ceuliniclrc» ln-oad. So I 

 took first rorliiiig-iilai' glass troiiglis of 4 cm. breadtli and ciystallising 

 dishes of 10 cm. diameter which \verc 11 lied widi meren it about 

 two centimetres deej). 



On the dry mercury I had lo pour a fairly large (|uanlily of 

 water before this would spread over (he whole surface; by means 

 of a pipette so much was drawii olf that only a very thin layer 

 remained. In this water the soaked or dry seeds were put. Tlie 

 seeds had to emerge for a great part above (he layei- of water; if 

 this latter was too thick they rotted and grew mouldy, es[)ecially 

 if the temperature was somewhat high, as in a hothouse. The dishes 

 were covered Avith glass or placed under a bell-jar in order to 

 prevent strong evaporation. Distilled water was used by preference. 



The seeds used w^ere: pea (Pisum sativum), garden-cress (Lepidium 

 sativum), wheat (Triticum vulgare), buckwheat (Polygonum Fago- 

 pyrum) and Lathyrus odoratus. The garden-cress grew quickest, so 

 that I could make a number of experiments in succession in a short 

 time with it. 



Most roots crept over the surface of the mercury or only pene- 

 tiated into it with their extreme tip. Sometimes however a radicle 

 had advanced to a fairly considerable depth. Thus on February 19, 

 1900, the radicle of a seed of garden-cress of two days was 7 mm. 

 long, of which 3 mm. were in the mercury. On March J 7, 1900, 

 se\eral radicles of garden-cress had, after three days, ad\'anced 4 I o 

 6 mm. })eri)en(licularly into the mercury, of a pea the radicle was 

 5 mm. in the mercury. On March 23, 1900, after thi-ee days, again 

 a few radicles of garden-cress were 5 mm. in the mercury. The 

 i-adicles that had found their way into it had for the greater i)art 

 had a downward directioii immediately at their germinatit)n, so that 

 only a short piece protruded abo\e the mei-cury. Sometimes however 

 roots of garden-cress, after having growii laterally about one centi- 

 metre, had still pierced the mercury 4 mm. with their a[)e\-. 



With wheat the three secondary roots crept over the mercury, an 

 apex seldom [.enetrated any length. Radicles of buclnvheat I did 

 not see penetrating. Lathyrus sometimes 5 to 7 mm. 



On further growth the i)lantlets that had pierced the mercury 

 were upset and were lifted out of the liciuid as was the case with 

 the great majority of seedlings at the very beginning. Hence (he 

 experiments \verc soon tinished. So the circumstance that the roots 

 turned black and died later and that the seeds rotted and grew 

 mouldy, ga\ e little trouble. The mercury howe\er had to be per- 

 fectly pure, since otherwise the radicles s(o[>ped growing too soon 



