832 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



1 he commonest plants illustrate well the prniciple of localized 

 Staines m development seen m the direct progressive develop- 

 ment ot the scedlmi;-. m localized stages of spring growth and in 

 the l(u ;ili/c(l st'iH'scence at flowering. It may be shown in a 

 vanctv nt \\a\ s. :\s noted in the present paper. In Thalictrum, 

 BaptisKi. etc.. It was shown especially by change in the number 

 ol leaflets; \\\ kuinex. bv the changes in the auricled base; in 

 l):uu us. etc.. b\ the change in the number of the teeth, and 

 tiii:ill\ Hi l aipaloi luin. l)v the presence or absence of the connate 



Dilfcicnt in(h\i(Uials show variations due to difterences in 

 aec ck-ration ot development. There is a differential acceleration 

 m iiuh\ idual seedlings, shown where the first nepionic leaf in 

 various iiuhvukials is more progressive or more retarded than in 

 the t\pKal eases. In spring growth it is also shown in much 

 the same wav, and with a still wider range of variation. These 

 diiti.ieiKes m aeeeleration may be caused by poor conditions, 

 suih pool soil luk ot sufficient moistuie, cold, etc., and by 

 mtunal cau>v.s not accounted for in the above. 



Kegressive de\ elopinent. seen in the localized senescence 

 below the llower. is shown in manv cases to be more reversion- 

 an ih 111 St i^, s 1,1 the usu d scullm^ W hen a large number of 

 seedlings .\uniiKd howcxci suth extreme (ases of varia- 

 tion ma\ be seen which would otherwise be overlooked. 



