DORSIVENTRAL INFLORESCENCES 



unilateral branching promotes a more frequent oscillation to and fro 

 than would otherwise be the case. Remembering the existence of grasses 

 with radial inflorescences we see in how great a number of ways the same 

 end can be arrived at in one and the same family. 



2. Entomophilous plants. In plants which occupy a position in which 

 they are subjected to a. unilateral strong illumination, as for example 

 on the edge of woods, and in inflorescences which grow on thick bushy 

 plants, the attractive apparatus of the flowers is more effective when it is 

 only turned to the one, that is the illuminated, side. I have elsewhere 

 pointed this out 1 and Urban 2 has further elaborated the point. The 

 most striking illustrations of this are to be found in cases where the 

 dorsiventrality of the inflorescence is determined in the primordia, and 

 of this I shall give an example. Fig. 83 represents a transverse 

 section through the bud of a flowering plant of Vicia Cracca. It has 



FlG. 83. Vicia Cracca. Transverse section through the end of a flowering shoot. S shoot-axis. Four inflores- 

 cences and six leaves are represented ; an inflorescence, 7/i arises in the axil of each of the leaves 3, 4, 5, and 6; 

 inflorescences do not however stand before the middle of their bracts but are towards the side of the chief axis 

 which is directed upwards. B the flowers of the older inflorescences; all the flowers stand upon the side turned 

 away from the chief axis. The pinnules of the older leaves are recognized by their involution ; st\-st t \ stipules 

 of which those upon the upper side are larger than those upon the under side. See also explanation of Fig. 78. 



two rows of leaves and the section has been made through leaves numbered 

 i to 6. The inflorescences, If, stand in the leaf-axils but they are all 

 turned to one side (in the figure directed upwards), because each is not 

 exactly in the median of the axillant leaf, but appears as displaced 

 towards a stipule 3 . In the leaf-axil upon the side turned away from the 

 inflorescence there appears later a vegetative shoot (see Fig. 79, page 126). 

 In each inflorescence the flowers are arranged upon the side turned away 



1 Goebel, Uber die Verzweigung dorsiventraler Sprosse, in Arb. d. bot. Inst. in Wiirzburg, ii 

 (1880), p. 399. 



3 Urban, Zur Biologic der einseitswenc'igen Bliilenstatide, in Ber. der deutsch. bot. Ges. 1885. 

 This is a primary position, not the result of a displacement. 



