( 132 ) 



deduced '), the figures of the crystal-sections for the section-planes 

 (P), {Q), and {H), then one finds tlie sections that are represented 

 in fig. 3. 



7T[i{o<o) 



Fig. 3. 



At tlie sections (P) and {(2) the traces of F (001) and .1/ (010) 

 inchide an obtuse angle, at (P) its supplement jt — 101°45' = 78°15'. 

 Whilst between the sections {F) and {Q) on the one side, {R) on 

 the other side a choice can easily be made, now the sections {P) 

 and {Q), at first sight looking identical, can be distinguished again 

 on account of their different double refraction. 



Botany. — "A few oh^ervatioiis on some, iiein ta/d i/'ttle knoini, cttsi's 

 of Leguininosae loith inechanicallij irrltahb' leaves." l»y S. H 

 KooKDEKs, at Buitenzorg. 



(Communicated in the meeting of May 27, 1911). 



Introduction. The observations here described were made 

 from 30 January to 13 February 1911 at Buitenzorg in the Botanical 

 garden, partly at older specimens, partly at young pot-plants. Although 

 other occupations took too much of my time to study these cases 

 in detail still I tliiid< them worth publishing, how incomplete they 

 mav be, for fi'om the literature at my disposition I must conclude 

 that the occurrenca of mechanically irritable leaves in the species 

 examined by me is either quite urdvuown or as yet not observed 

 at Buitenzorg. 



§ 1. A 1 b i z z i a s t i p u 1 a t a Benth. — The first observation on 

 movements of the leaflets (foliola) after vigorous tapping was made 



1) Proc. Royal Acad. Amst. 1911, p. 1033. 



