242 THE DIRECTION OF MOTION. 



served. * " : ' : " * In this prevailing spiral form of organic 

 bodies, therefore, it appears to me, that there is presented a 

 strong prima facie case for the view I have maintained. 

 * * * The spiral form of the branches of many trees is 

 very apparent, and the universally spiral arrangement of the 

 leaves around the stem of plants needs only to he referred 

 to. * ' :: ' * The heart commences as a spiral turn, and in 

 its perfect form a manifest spiral may be traced through 

 the left ventricle, right ventricle, right auricle, left auricle 

 and appendix. And what is the spiral turn in which the 

 heart commences but a necessary result of the lengthening, 

 under a limit, of the cellular mass of which it then con- 

 sists? " * * * 



" Every one must have noticed the peculiar curling up of 

 the young leaves of the common fern. The appearance is as 

 if the leaf were rolled up, but in truth this form is merely 

 a phenomenon of growth. The curvature results from 

 the increase of the leaf, it is only another form of the 

 wrinkling up, or turning at right angles by extension under 

 limit.' 3 



" The rolling up or imbrication of the petals in many 

 flower-buds is a similar thing; at an early period the small 

 petals may be seen lying side by side, afterwards growing 

 within the capsule, they become folded round one an- 

 other/' * * * 



" If a flower-bud be opened at a sufficiently early period, 

 the stamens will be found as if moulded in the cavity be- 

 tween the pistil and the corolla, which cavity the anther- ex- 

 actly till; the stalks lengthen at an after period. I have 

 noticed also in a few instances, that in those flowers in which 

 the petals are imbricated, or twisted together, the pistil is 

 tapering as growing up between the petals; in some flowers 

 which have the petals so arranged in the bud as to form a 

 dome (as the hawthorn; e. g.), the pi-til i< flattened at the 

 apex, and in the bud occupies a space precisely limited by 

 the -taniens below, and the enclosing petals above and at 



