( 208 } 



conclusion iiiay be supported l\v (|nantitative (leterniiiuitions, bul these 

 are not necessary in order to proA^e its correctness. 



The shrubs of Thea assamica of the Agricultural Garden at 

 Tjikeumeuh bear a number of variegated leaves often so discoloured 

 that one side of the midrib is yellow whilst the other side is green. 



These two sections which are of course, equally old and exactly 

 similar and which differ only l\y the absence or presence of choro})hyll, 

 were compared as to their amount of caffeine. The operation was 

 conducted in the manner previously described ^) for catechol. 



Of a small number of leaves a yellow and an etpially large green 

 piece was taken, both were triturated separately with quick lime, 

 extracted with the same amount of alcohol and the deposits ol)tained 

 by sublimation w^ere then compared. 



Each time the sublimates obtained from the yellow part of the 

 leaves were found to be much denser; the part free from chIor(t[>hy 11 

 consequently contains decidedly more caffeine than the one containing 

 chlorophyll ; a very significant fact w^hich may enable us to get a 

 better insight into the chemical processes of this plant. 



At the end of this preliminary' communication we desire to Ihaidv 

 Prof. VAN R0xMBUK(;n acling director of the Botanical Gardens at 

 Buitenzorg, for his kind assistance. 



Mathematics. — ''Rcctlfn'uKj curirs." By Mr. .J. van uEGiuHNüJr. 

 communicated by Prof. J. Caudinaal. 



It is known that every motion of an invariable plane system can 

 be regarded as the rolling of a detinite curve of the moving sj^stem 

 (the "movable [)olar curve") over another definite curve of the 

 immovable plane (the "fixed polar curve"). In the following paper the 

 special case will be treated of this general motion, where the moxable 

 polar curve is a right line and the motion therefore consists in the 

 rolling of one of the tangents of the tixed polar curve over that curve. 



Here, however, the constant polar curve itself will not be given ; 

 according to a stated law (see N". 1) this will ha\'e to be deduced 

 from another curve given in the moving plane (its rectifying curve) 

 which takes its place and determines it by means of the rectilinear 

 movable polar curve. The replacement of the fixed polar curve b}^ its 

 rectifying curve \vill give rise to the advantage that in some cases 

 the rectifying cur^'e \vill be a much simpler one than the rectified 



ij Investigations of glucosides in connection willi tlic internal mutation of plants. 

 Septembei- 1902, 



