SWEET-CLOVER SEED. 



attached to the staminal tube, the petals may be bent downward 

 sufficiently far so that many different kinds of insects may secure 

 without difficulty the nectar secreted around the base of the ovary. 



The fingerlike processes of the alse are appressed closely to the 

 carina, therefore the alse are bent downward with the carina by 

 insects. These processes grasp the staminal tube superiorly and 

 tightly when the carina and alas are in their natural positions, but 

 when the carina is pressed downward by insects the fingerlike proc- 

 esses open slightly but not so far that they do not spring back to their 

 original position when the pressure is 

 removed. The staminal tube splits 

 superiorly to admit the tenth free 

 stamen. The filament of this superior 

 stamen lies along the side of this 

 staminal tube. The filaments of the 

 nine stamens which compose the stami- 

 nal tube separate in the hollow of the 

 carina. All stamens bear fertile an- 

 thers. The pistil is in the staminal 

 tube, the upper part of the style and 

 stigma of which is inclosed with the 

 anthers in the carina. The stigma 

 is slightly above the stamens. 



An insect inserts its head into a 

 sweet-clover flower between the vexil- 

 lum and carina, the stigma, therefore, 

 comes into direct contact with the 

 head of the insect and cross-pollination 

 is effected. At the same time the an- 

 thers brush against the insect, so that 

 its head is dusted with pollen, to be 

 carried to other flowers. 



Fig. 2. — Lengthwise sectional view of a very 

 young flower of Melilotus alba, showing the 

 relative development of the stamens and 

 pistil. In the upper set of stamens the di- 

 visions of the mother cells are completed, 

 while division is just beginning in the 

 lower set of stamens. In the ovules the 

 outer integuments are well started on then- 

 development, a, Anther; o, ovule; p., 

 pistil. X38. 



DEVELOPMENT OF THE FLORAL ORGANS OF SWEET CLOVER. 



The stamens of Melilotus alba and M. officinalis may be divided 

 into two sets, according to their length and time of development. 

 (Fig. 2.) The longer set extends about the length of the anthers 

 above the shorter set, and the pollen mother cells in the longer set 

 divide to form pollen grains at least two days earlier than those in 

 the shorter set. At the time the pollen mother cells divide, the 

 longer set of stamens is approximately three-eighths of a millimeter 

 in length and the pistil about half a millimeter long. The stigma 

 and a portion of the style project beyond the stamens, and this rela- 

 tive position is maintained to maturity. The pollen mother cells 

 undergo the reduction division while the megaspore mother cells are 



