64 



THE CAUSES OP FLUCTUATIONS IN TURGESCENCE 



place of being elevated they 



are now 



Somewhat later, and just before nyctitropic movements begin to appear, the folded pinnae 

 still remain only very slightly divergent, but 

 permanently depressed, the midribs slop 

 the primary petiole 



cr 



downwards and forwards from the line of 



and having 



th 



ke 



directed downward 



of outwards 



(Plate III, Fig 



of pulvinar parenchj 



the outer su: 

 diurnal elev 



The secondary p 



now show distinct 



dence of an accumulat 



over the anterior surface basally and along the entire length of 

 face. Movements soon begin to appear and to lead to gradually increasing 



divergence and expansion of the pinnae 



alternating 



pression, convergence, and folding up of the laminae. Somewhat 1 

 permanently expanded, and at the same time alternating movem 



d of convergence and depression go 



with nocturnal de- 



the laminae become 



of divergence and 



g in amount. At this period 



pinnae during the day 



lely divergent, and have their upper surfaces appr 



imatcly in 



same plane as the upper surface of the rachis (Plate III, Fig 



d 



very closely convergent and depressed 



& 



,tly that their upper surf; 



are 



tical to the line of the rachis and look directly forwards toward 



apex. The noctui 



position at this stage may be regarded simply as the result of extreme 



convergence 



and depression without any appreciable 



Rotat 



and, for a time, goes on gradually increasing until, for a period 



of the lamina, however, soon 



the upper surfaces 



of the p 



come to look directly inwards fac 



one 



Dther 



ill 



movements attain their maximum development, and it is 



s is the period at 

 lcceeded by one in 

 The diminution in rotation causes the upper 

 faces of the laminae nocturnally once more to be directed more and more forwards, 



hich they undergo gradual diminution 



they do so to a position more or less like th 



of development. The ] 

 the coincident diminut 



prop 



to 



an earlier stage 



ho 



is not 



in 



ih the pr 



convergence 



and dep 



ment, 



d th 



mplete, as it is interfered with by 

 •ession. Finally, a period arrives at 

 complete abolition of all appreciable move- 

 e pinnae remain permanently fixed in what was previously the diurnal 



diminution leads 



position, with the upper surfaces of 



nun 



of the rachis or slightly ascending from it, and their midribs at 



looking directly upwards in the 



somewhat inclined backwards towards the base of the leaf 



right 



angles 



to 



or 



On examining the secondary petiole of 



pinna at the period at which 



mov 



are at their maximum, two distinct masses of pulvinar tissue may be recognised in it. 

 They differ from one another in tint, the one having an ochreous tin<re. whilst the other 



pure green, and they are arranged in 



The ochreous tissue 

 it becomes purely ei 



the base of the pulv 



a peculiar spiral fashion (Plate III, Fig. 



2 



whilst the green tissue basally 



lies antero-external, and fartl 



out 



the laminar extremity invades the anterior surfac 



purely 



midrib 



a with the mass of green parenchyma which forms 

 The pulvinus extends for some distance 



of the pul 



rid 



o 



llary, but towards 

 so as to become 

 • the course of the 



under-surface, and the g 



into the base of the lamina on tin- 



amount than the ochreous tissue on the other side 



the inner side of the midrib 



is more 



picuous 



It is this 



piral disposition of the opposed 



determines the peculiar character of the 



masses 



movements of the pinnae. W 



f pulvinar parenchyma that 



the develop 



is subsequently distin 



Z11 X \ ^^ ^ bfc ^ the f ^ that the tissue, which „ n^^ _ 



anfco™ the P™«it Session 



and convergence of the pinna which prevails immed 



tely antecedent to the period 



which 



