DEVELOPMENT OF PLANTS 439 



305). The receptacle is frequently elongated and consequently 

 the organs of the flower, especially the sporophylls, are numerous 

 and indefinite in number and spirally arranged. Were it not 

 for the perianth, such a type of flower would be quite as primi- 

 tive as any of the preceding orders. 



(a) The Buttercup, Ranunculus. — -The flower of the buttercup 

 illustrates the more characteristic features of the Ranales (Fig. 

 305, A, B). Here the perianth is apparently differentiated 

 into calyx and corolla. The petals, however, are sometimes 

 regarded as stamens that have become highly modified for the 

 production of nectar. The sporophylls are indefinite in number 

 and spirally arranged. It is interesting to note the relationship 

 of the various parts of this simple flower and their behavior during 

 the period of blooming. When the flower first opens, the anthers 

 are still closed and clustered around the receptive stigmas, afford- 

 ing a natural landing place for the insects (Fig. 305, B). Thus 

 crossing may only be effected with the spores carried from older 

 flowers. At a later period the outermost filaments elongate, 

 curving over towards the petals, so that as their anthers discharge 

 there is little chance of autogamy (Fig. 305, C). This position 

 also brings the anther into the pathway leading to the nectar 

 gland at the base of the petal (Fig. 305, D), so that the insect 

 in probing for 'the nectar is sure to receive some of the sticky 

 microspores on his body. Each day, for about a week, succes- 

 sive series of stamens behave in this manner, and it is not until 

 the innermost anthers are discharging on the last day of bloom- 

 ing of the flower that there is an opportunity for autogamy. In 

 many members of this and other orders you will find that the 

 stigmas and anthers of the innermost stamens actually meet, 

 owing to the peculiar curvature of the styles and filaments, thus 

 ensuring autogamy in case crossing has failed. It should be 

 borne in mind that the devices for effecting autogamy, as a last 

 resort, are quite as general and often as elaborate as the pro- 

 visions for bringing about crossing. The microspores are pro- 

 tected against dews and rains by the folding of the perianth and 

 also by the downward curvature of the pedicel at night, whereas on 

 each succeeding bright day the perianth opens again and the 



