4 Esther Pearl Hensel 



OPEN A.M. CLOSED P.M. 



Sisyrinchium angustifoliufn WxWtx 9:30-11:00 5:00-6:45 



Tradescantia bradeata L. 5:00- 6:00 4:00-5:00 



II. Night bloomers. open p.m. closed a.m. 



3. Opening and closing repeatedly. 



*Menizelia mida (Pursh.) T. & G. 4-5 days 3:00-5:00 5:00- 6:00 



4. Opening and closing but once. Iday or less. 



Allionia linearis Vnr^h. 5:00-6:00 8:00-9 00 



Allionia nydagitiea Wxchx. 4:00-5:00 9:00-10:00 



Cereus grandijlorus 'MiW. 8:00-9:C0 2:00-3:00 



Datura siranwnium "L. 5:00 6:00 8:00-11.03 



*Jpoinoea purpurea (L.) Ro\.\\. 4-5 a.m. 10:30 a.in.-o p.m. 



*Mirabilisjalapa'L. 6:00-9:00 10 a..m.-4p.m. 



Onagra biennis {U) Sco'p. 5:00-6:00 9:00-10:00 



*Pachylophus caespito.as {^\M.) R7\.\m:\nn 5:00-8:00 9:00-11:00 



Silene/ia/lii Wats. ' 5:00-7:30 9.00-12.00 



All flowers not included in the previously stated types stay 

 open through the day and night during their period of existence. 

 Such flowers do not open because of temperature changes but 

 because they have reached a certain period of growth ; the largest 

 number of flowers belong here. Of the other classes, a very large 

 number are day bloomers, a smaller number night bloomers. 



Ephemeral flowers behave much as those flowers which open 

 and close for several days, that is, they are influenced by temper- 

 ature variations ; in their opening, however, they show a close 

 relation to the large number of flowers which open only once 

 and stay open until they die (generally after several days) ; the 

 chief difference is that the ephemeral species are more regular 

 in the time at which this process occurs. 



HISTORICAL REVIEW (FROM l686 TO I905) 



So much has been written on the subject of flower movement, 

 and. with such different vievv^s" as to its cause, that it seems ad- 

 visable to give a rather detailed account of the work of the dif- 

 ferent investigators. 



Pfeffer reports Cornutus as having said as early as 1686 that 

 heat caused, or at least hastened, the opening of the anemone. 



194 



