QUANTITATIVE INFLUENCE OF CORRELATION 



211 



I have elsewhere l pointed out that the size 

 attained by a leaf may be dependent upon corre- 

 lation with its shoot-axis. In illustration of this we 

 have the behaviour of many climbing plants in which 

 the rapid and strong elongation of the internodes 

 causes a transient or permanent arrest of the develop- 

 ment of the leaves. The smallness of the leaves of 

 etiolated shoots is, at least in many cases, no direct 

 result of the influence of light, because if the upper 

 part of a shoot of Phaseolus multiflorus is confined 

 in a dark chamber, and only one leaf is left upon it, 

 and at the same time all the vegetative points of 

 shoots are removed from it at an early period, 

 the leaf in the dark attains the same size as the 

 leaves on the part of the shoot in the light 2 . 



It is probable that similar correlations also 

 exist between the leaf-structures in the flower. In 

 the flag-apparatus formed by the peripheral flowers 

 of the inflorescence of many Compositae, in Vi- 

 burnum Opulus, and species of Hydrangea, the 

 corolla, or in the case of Hydrangea the calyx, 

 becomes greatly enlarged whilst the stamens and 

 carpels are either functionless or entirely wanting, 

 and the conjecture is fully justified that a direct 

 compensation occurs here, in other words, that the 

 growth of the corolla or calyx causes the arrest or 

 abortion of the sporophylls. It is true this com- 

 pensation has not been experimentally proved, but 

 other similar cases make its existence likely. Such 

 similar cases are found, for example, in the abortion 

 of the whole flower as we see it in Muscari comosum, 

 the fasciated garden-form of Celosia cristata, the 

 cauliflower and other cases. In Muscari comosum 

 the higher flowers of the inflorescence form the 

 flag-apparatus, their stalks are much longer than 

 those in the lower inconspicuous flowers and are 

 coloured blue, and the sporophylls are arrested in 



FlG. i io. Latliyrus Aphaca. 

 Seedling plant. The lamina 

 is developed on the two lower 

 foliage-leaves only, and the 

 stipules are much smaller in 

 these leaves than in the suc- 

 ceeding ones in which the 

 lamina is suppressed ; higher 

 upon the stem tendrils replace 

 the leaves. 



1 Goebel, Pflanzenbiologische Schilderungen, i. p. 236. 



2 Jost, tiber die Abhangigkeit des Laubblattes von seiner Assimilationsthatigkeit, in Pringsh. 

 Jahrb. xxvii. See also with reference to phenomena of etiolation Godlewski, Zur Kenntnis der 

 Ursachen der Formanderung etiolierter Pflanzen, in Botan. Zeitung, 1879, p. Si. In the cultivation 

 of the tobacco-plant the size of the leaves is greatly increased by topping of the chief shoot and 

 removal of the lateral branches ; see Wollny, Untersuchungen iiber kiinstliche Beeinflussung der 

 inneren Wachstumsursachen, in Forschungen auf dem Gebiete der Agrikultnrphysik, viii. 



P 3 



