THE LEAF. 



189 



upper and female sporophylls in the lower part of the 

 cone. 



Licopoli observed, in flowers of Melianthus in which 

 calyx and corolla were absent, bracts taking their place, 

 and that these were antheriferous. 



11. — Oarpellody of Bliaots. — C. Schimper observed 

 leafy bracts of the cabbage which bore ovules. 



(Ersted describes the occurrence of an ovule or 

 ovules on the lower side of a bract in a female cone 

 of Picea nigra (PI. XIII, fig. 6). 



Lutz found in Crocus stigmatiferous bracts. 



12. — Simplification of Foliage. — Instances of this 

 phenomenon are much rarer than the converse one : 

 the change from simple into compound leaves. And 

 this fact constitutes one of the pieces of evidence in 

 favour of the view that the latter is reversionary in 

 character, for it is a pretty-generally admitted fact 

 that disturbances in the organism tend to cause the 

 re-emergence of otherwise latent ancestral characters. 



The bi pinnate leaves of the honey-locust tree 

 (Gleditschia triacanthos) may become either wholly or 

 partially pinnate ; in the latter case a portion of the 

 frond may be bipinnate, the other portion simply 

 pinnate. Or, the simplification may proceed still 

 further : division of the leaf may totally disappear and 

 the leaf become completely simple. Or again, there 

 may be a compromise between the two extremes ; half 

 the leaf on one side of the rachis may be bipinnate, 

 and the other longitudinal half consist of a single 

 unsegmented lamina. Perfectly simple leaves have 

 also been seen in Robinia Pseud-acacia. 



In the same way the ternately-compound leaf of 

 Phaseolus may be replaced by a simple one ; and this 

 also occurs in similar leaves of plants of other orders, 

 e. g. the strawberry (Fragaria vesca) giving rise to the 

 variety monophylla, originally produced in 1761 at 

 Versailles as a seedling-sport. 



In some other plants, e. g. the ash (Fraxinus excelsa) 

 and the elder {Sambucus nigra) ,the pinnately-compound 



