Contents 



xvn 



LECTURE PAGE 



Purple leaves. Celosia. Italian poplar. 

 Cactus dahlia. Mutative origin of Dah- 

 lia fistulosa, and Geranium pratense *in 

 the experiment-garden. 



XXII. Systematic atavism 630 



Reappearance of ancestral characters. 

 Primula acaulis umbellata. Bracts of 

 crucifers. Zea Mays cryptosperma. 

 Equisetum, Dipsacus sylvestris torsus. 

 Tomatoes. 



XXIII. Taxonomic anomalies 658 



Specific characters occurring in other cases 

 as casual anomalies. Papaver brac- 

 teatum monopetalum. Desmodium 

 gyrans and monophyllous varieties. Pel- 

 tate leaves and ascidia. Flowers on 

 leaves. Leaves. Hordeum trifurcatum. 



XXIV. Hypothesis of periodical mutations . . 686 

 Discovering mutable strains. Periods of 

 mutability and constancy. Periods of 

 mutations. Genealogical trees. Limited 

 life-time of the organic kingdom. 



F. FLUCTUATIONS. 



XXV. General laws of fluctuations .... 715 

 Fluctuating variability. Quetelet's law. 

 Individual and partial fluctuations. 

 Linear variability. Influence of nutri- 

 tion. Periodicity-curves. 



XXVI. Asexual multiplication of extremes . . 742 

 Selection between species and intra-spe- 

 cific selection. Excluding individual 



