170 



PRINCIPLES OF PLANT-TERATOLOGY. 



of the strawberry (Fragaria vesca) in which four leaflets 

 were formed by splitting of one of the two lateral leaf- 

 lets, and there is a quinquefoliolar variety of F. grandi- 

 flora. The leaf of various species of clover, e. g. Tri~ 

 folium pratense and T. repens, is known to produce not 

 infrequently four leaflets instead of three (PI. XV, 

 fig. 1), and more rarely five (fig. 47 a), six, and even 

 seven leaflets. Of this case there seem to be two 

 types: (1) in which the seven-fold leaf is obviously 

 derived by fission of the three normal leaflets, which 

 are arranged in groups of three each in the position 



y IQm 46. — JJlmus sp. Forking leaf with midrib but not lamina 

 completely divided. (G. S. Saunders.) 



in which they were formed ; in (2) the leaflets are 

 scattered along a developed rachis and constitute an 

 imparipinnnate leaf, so that the exact mode in which 

 they arose by fission is no longer clear (fig. 47 6). It 

 is stated that the Dutch clover (Trifolium repens) may 

 occasionally produce pinnate leaves with as many as 

 ten leaflets. Pinnate leaves may also occur in other 

 genera with trifoliolate leaves belonging to the same 

 tribe, as in lucerne (Medicago sativa), melilot (MeliJotus 

 alba), and bird 5 s-foot trefoil {Lotus major). In Fra- 

 garia elatior, F. eollina, and F. virginiana, Magnus 

 and others describe the appearance on the leaf-stalk, 

 some distance away from the large normal leaflets, of 

 several small auricles, representing the same imper- 

 fectly-developed lateral leaflets as occur normally in 



