143 



90. Bidens trichosperma (Michx.) Brhton. Tickseed SunHower. 



{Coreopsis trichospei-via Michx.) 

 Occurs sparingly in Monroe county in swamps along the bottom lands 

 of Bean Blossom Creek. August 10, 1886. 



Recorded in B. & C. Flora from Jefferson county. 



91. Hyrtienopappus caroliniensis (Lam.) Porter. 



{H. scabios<eus L'Her. ) 



Found sparingly on the side of a sandy ridge northeast of Seventh 

 Street Bridge across Lost Creek, Vigo county. May 31, 1890. 



The first record for the Slate, its.range being given in the Manual as 

 "Illinois and Southward." 



92. Senecio lobatus Pers. Butterweed. 



Taken on several occasions in 1891 and 1892 from low, damp places 

 about ponds and ditches in Vigo county. The first Indiana record, its 

 Manual range being "North Carolina to Southern Illinois, Missouri and 

 Southward." 



93. Lacfum hirsuta Muhl. Hairy Wild Lettuce. 



(Laduca sanguinea T. & G.) 

 Borders of prairies and dry, sandy fields in Vigo county; scarce. 

 Recorded from Gibson countv by Dr. Schneck. 



Periodicity of Root Pbesscre. By M. B. Thomas. 



The fact that the roots of plants absorb water and force it up through the 

 stem, producing bleeding whenever the stem is injured, was discovered by Hales 

 in 1721, and since that time numerous investigators have examined this phenom- 

 enon of root absorption in a more or less exhaustive way until we have to con- 

 cern ourselves only with an inquiry into its daily variations and see if there is 

 not some law governing the changing phenomenon that will give us a more com- 

 plete insight into this important physiological problem in plant growth. 



The general matter of the periodicity of root pressure in forcing water through 

 stems in opposition to gravity was studied by Sachs, and his observations form a 

 basis for our present work. He made experiments regarding the time of maxi- 

 mum and minimum pressure with a few common plants, and his results are too 

 well known to need extended description. The conclusions of his experiments 

 have been to fix the time of maximum pressure at 9-11 A. M., with a decrease 



