IMPARIPINNATE LEAVES IN CASSIA. 



141 



had either three terminal leaflets or two pairs very close together. 

 Fiftv-two were assigned to the form with three terminal leaflets 

 and twenty-eight to that with four. Almost all of these leaves 

 were tvpical representatives of these forms as we have described 

 them. Among those with two approximated terminal pairs one 

 was found in which the two pairs were slightly separated, an- 

 other in which the terminal of the two pairs was of leaves only 

 about half as large as the others, and in a third case one of the 

 two terminal leaflets was only about half so long or wide as the 

 other ; but except for these slight deviations all had the four 

 terminal leaflets closely approximated and of about the same size. 



Fig. 20. Cassia. A. terminal leaflets in a normal paripinnate leaf; B. 

 anomalous type with four approximated terminal leaflets; C, three terminal 

 leaflets in an apparently imparipinnately compound leaf; D, transitional 

 form in which one of the two terminal leaflets is considerably reduced in 

 size. 



Among: those with three leaflets the terminal one was in a few 

 cases much smaller than the others, but generally it was of about 

 the same size. The terminal scale was not alwa_\s to be seen but 

 could usually be made out. ( )ccasionally there appeared a scar 

 or scale indicating the existence of a priiuordium for another 

 leaf. The origin of the terminal leaflet could in most cases be 

 detenuined only froiu the evidence offered by the identity of 

 form and insertion of the petioles in those with three and four 

 terminal leaflets, and the presence of the terminal scale. In no 

 case was satisfactory evidence obtained for the derivation of the 

 terminal leaflet from the end of the rhachis. 



