THE SHAPES AND ARRANGEMENTS OF FLOWERS. 609 



directions as to get the most light ; and in other cases their shoots 

 were led to take directions almost or quite horizontal. That, along 

 with these modifications in the directions of their shoots, there went 

 adjustments in the attitudes of their leaves, was a fact not specially 

 worthy of remark ; for plants placed inside the windows of houses 

 habitually show us that leaves quickly bend themselves into atti- 

 tudes giving them the greatest amounts of light. But the fact 

 which attracted my attention was, that the flowers changed their 

 attitudes in an equally-marked manner. The radial distribution 

 passed into a bilateral distribution with the greatest readiness. 

 Comparison of the annexed figures will show the character of this 

 change. 



Figure I. represents part of a vertically growing shoot. This 

 belonged to an individual growing unimpeded by bushes, and getting 

 light on all sides. Here it is observable that the pairs of leaves, 

 placed alternately in directions transverse to one another — one pair 

 pointing, say, north and south, and the next pair pointing east and 

 west — maintain, taking them in the aggregate, a radial distribution ; 

 and it is also observable that the alternate pairs of flowers are 

 similarly arranged. 



Figure II. is a sketch from a shoot which leaned towards one 

 side, and of which the higher part, as it bent more and more, 

 got its upper side more and more diiferently conditioned from its 

 lower side. Here we find that not only the leaves, but also the 

 flowers, have adjusted themselves to the changed conditions. The 

 leaves of the lowest pair hang out in the normal way, on the op- 

 posite sides of the axis, so that a plane passing through their sur- 

 faces will cut the axis transversely ; and their two axillary flower- 

 buds, c and d, are similarly placed on opposite sides of the axis. 

 But at the other part of the shoot, we see both that the leaves have 

 adjusted themselves so that their planes, no longer cutting the axis 

 transversely, keep a fit adjustment with respect to the light ; and 

 also that the flowers, no longer on opposite sides of the axis, have 

 bent round to the upper side, as at a and b. 



Figure III. shows us this re-arrangement carried still further. 

 The shoot it represents was growing in a direction nearly horizontal, 

 and therefore receiving the light only on one side. And here, 

 besides seeing that the leaves have so adjusted themselves that they 

 all lie in approximately the same plane, which is parallel to the axis 

 instead of transverse to it, we see that the two pairs of flower-buds 

 have both come round to the upper side of the axis. So that 

 in this shoot, the original radial symmetry in the arrangement 

 of leaves and flowers, is completely changed into a bilateral 

 symmetry. 



These facts do not, it is true, prove any modification in the forms 

 85 



