270 MISCELLANEOUS OBJECTIONS TO THE [Chap. VT1 



sixth stamen standing opposite to a petal being alone 

 developed ; and this stamen is not present in the ordi- 

 nary flowers of these species ; the style is aborted ; and 

 the ovaria are reduced from three to two. ISTow although 

 natural selection may well have had the power to pre- 

 vent some of the flowers from expanding, and to reduce 

 the amount of pollen, when rendered by the closure of 

 the flowers superflous, yet hardly any of the above special 

 modifications can have been thus determined, but must 

 have followed from the laws of growth, including the 

 functional inactivity of parts, during the progress of the 

 reduction of the pollen and the closure of the flowers. 



It is so necessary to appreciate the important effects 

 of the laws of growth, that I will give some additional 

 cases of another kind, namely of differences in the same 

 part or organ, due to differences in relative position on 

 the same plant. In the Spanish chestnut, and in certain 

 fir-trees, the angles of divergence of the leaves differ, 

 according to Schacht, in the nearly horizontal and in 

 the upright branches. In the common rue and some 

 other plants, one flower, usually the central or terminal 

 one, opens first, and has five sepals and petals, and five 

 divisions to the ovarium ; whilst all the other flowers 

 on the plant are tetramerous. In the British Adoxa the 

 uppermost flower generally has two calyx-lobes with the 

 other organs tetramerous, whilst the surrounding flowers 

 generally have three calyx -lobes with the other organs 

 pentamerous. In many Composita? and Urnbelliferae 

 (and in some other plants) the circumferential flowers 

 have their corollas much more developed than those of 

 the centre ; and this seems often connected with the 

 abortion of the reproductive organs. It is a more 

 curious fact, previously referred to, that the achenes 



