OEGAXS OF NTJTEmOX. 



135 



Fig. 260. 



Fig. 261. 



Fig, 26a Wliorled leaves of a species of GoUum. Fig. 261. Decussate 



leaves of the Pimelea decussaUu 



frequently happens that a somewhat similar arrangement occurs, 

 thus the leaves of one whorl correspond to the intervals of the 

 whorl below it. There are however commonly great irregu- 

 larities in this respect, and in some cases the number of leaves 

 in the different whorls vary, by which their arrangement be- 

 comes still more complicated. This is the case for instance in 

 Lysimachia vulgaris. 



Only one leaf can arise from the same point, but it sometimes 

 happens that by the non-development of the internodes of an 

 axillary branch aU the leaves of that branch are brought in 

 contact, in which case they form a tuft ov fascicle {fig. 202), and 

 the leaves are then said to be tufted or fascicled. Such an ar- 

 rangement is well seen in the Barberry 

 and Larch. That fascicled leaves are 

 thus produced is rendered evident by 

 the fact, that in the young branches of 

 the Larch the internodes become elon- 

 gated and the leaves consequently sepa- 

 rated from each other. 



The laws which regulate the arrange- 

 ment of leaves upon the stem have of 

 late years been carefully investigated ; 

 and when we consider that all the organs 

 of the plant which succeed the leaves are formed on the same 

 plan as them, and follow similar laws, the determination of 

 these laws must be considered to be a matter of much import- 

 ance. It has been supposed by some that the arrangement of 

 the leaves varies in the different classes of plants : thus, that 

 in Dicotyledons where the cotyledons or first leaves which are 

 developed are opposite, that the regular arrangement of the 



Fig. 262. 



Fig. 262. Fascicled or tuft- 

 ed leaves of tbe Larch. 



