THE AMERICAN NATURALIST. [Vol. XXXVII. 



The lobes are frequently progressively reduced to three and in 

 rarer instances to the simple form shown at the base of spring 

 growth. Here then where there is no flower to take the strength 

 of the plant from the leaves, the diminutions of growing strength 

 near the end of the season is sufficient to bring out regressive 

 characters. 



Arabis albida. Figs 20-37. 

 The seedlings of this plant have after the cotyledons a simple 



rounded-oval leaf rounded at the base, Fig. 20. The second leaf 

 is broadly ovate with the widest part at about the middle, four 

 slight notches making two teeth on each side, very slightly 

 raised from the general outline and an auricled base, Fig. 2 1 . 



The third leaf is broadest nearer the base, more pointed and 

 with three teeth on each side, the base auricled, F"ig. 22. The 



