214 The Botanical Gazette. [July, 
As the root absorbs water the pressure upon the column of 
ous spiral course on the cylinder. As the cylinder revolves 
once each hour the hourly variation can be studied by observ: 
ing the distance between the lines. 
The supply of water given to the plant is kept constant by 
means of a flask of water supported by a stand and having an 
exit tube touching the surface of the water in the dish in 
which is placed the jar containing the plant. 
The apparatus can be made in sizes appropriate for the 
study of periodicity of root pressure in almost any plant. 
An eight day clock should be used and the apparatus need 
scarcely be touched until the plant is exhausted. The differ- 
ence between the maximum and minimum variation will grow 
less as the column of mercury becomes higher but the time of 
variations will be the same for each day. 
€ apparatus described may be constructed at a very 
On the apical growth of the stem and the development of 
€ sporangium of Botrychium Virginianum. 
Cc. L. HOLTZMAN. 
(WITH PLATE XVI.) t 
__ The origin and affinities of the Filicine is one of the nee 
‘mportant problems of systematic botany. Among avers 
tions directed to solving this problem not least have of 
those concerning the origin of the Filices and the ree 
the eusporangiate and leptosporangiate groups. It a | se- 
advocated by some that the Ophioglossee form a natura 
