98 



tube aiv liii'LTc, there behm no sii-e:uiis oi tiny lml)liles ns in the case of 

 the watei- ])Iants. 



The fate <if the evolntinn nf the uas deiieiMls (in tlie hri.i,'litness nt" the 

 li.Liht and the supiily of carhdn dioxide. If a iiai't of the li.u'ht is sluit otif 

 tlie rate hecdnies sh)\ver and tlu' evohition of gas ceases when tin- li.iiht 

 becomes dim. The rate bi-ecanes slower if tlie bubblins of carbon dioxide 

 tJuon.i,di tlie water is stojiped. Enonyh carlion dioxide diffuses into the 

 water from the air for tlie evolution of gas tu go on slowly. l)nt a rapid 

 evolution is not obtained unless the water is kept charged with the carlion 

 dioxide. 



In ()ne experiment leaves of Melilotiis were diiijied for an histant 

 into ~>ty/( alcohol and then immediately immersed in water. These leaves 

 became wet, no film of air was present and no evol',iti(ai of gas occurred 

 though the ]ilants were exjtosed to the sunlight for more than six hours. 



These ( x])(>riments were performed in May ot lUlll. after which time 

 nothing further was d<ine excejtt that in October Mclil'ifiis and Xcixtfi 

 were used in demonstration experiments before a class. A good quantity 

 of gas AVIS obtained. The rate of evolution was slower than in May, 

 probably due in jiart to- difference in light and pait to ditfeiH'uce in the 

 condition of the i)lants. The plants used in May were young vigorous 

 .shoots, while only old plants could be found in October. 



As a plant to use in denmnstrating the evolution of oxygen in photo- 

 syuthesis, I .am (|uite sure that either Melilotiis or Xcjirhi will prove en- 

 tirely satislactnry. They are not only much easier to obt.iin than the 

 a(iuatic jilants. which are snid to be necessary foi- this experiment, but the 

 results are more quickly attained and are more striUiiig than is usually the 

 case with the conventional aipnitics used Uw this purpose. 



Ihl'ainr riiircrxitu, 

 (IrcciKdsllc, 1)1(1. 



