1 882.] and Cassia chamcecrista. 283 



right-handed, and those in which it turns to the left, left-handed. 

 The figure represents a left-handed flower. With a little exami- 

 nation, it is found that there is a very simple law deciding whether 

 any given flower, from its position, should be right-handed or left- 

 handed. In the examination of scores of flowers I found no 

 exception to this law. The flowers are arranged in simple, bract- 

 less racemes, which extend in a horizontal position. The flowers, 

 consequently, are arranged on each side of the axis. 



The law referred to is this. The pistil, in any flower, turns to- 

 wards the axis of the raceme. It follows from this, that succes- 

 sive flowers on the same raceme have their pistils turned toward 

 opposite sides. It is also a fact of observation, that the flowers of 

 a cluster on any one branch, and opening about the same time, are 

 either all right-handed or all left-handed. Any plant, however, if 

 it is at all large, exhibits right and left-handed flowers in about 

 equal numbers. 



Of five plants observed : 



No. 1 had 5 pistils left-handed_ and 4 right-handed. 



The advantage in all this is so obvious that it scarcely needs 

 explanation. It is like most irregularities in flowers, a contri- 

 vance for cross-fertilization. After considerable watching, I had 

 noticed no insects visiting the flowers, except a small humble-bee, 

 and this seemed quite attentive. The weight of the bee so springs 

 down the flower, that it is quite difficult, on account of the large 

 flexible corolla, to see just what is done, but repeated observations 

 led me, quite satisfactorily, to this conclusion. The bee seeks the 

 pollen — for the flowers have neither nectar nor odor — and this she 

 uniformly gets from the four shorter stamens; never, so far as I 

 could determine, from the larger one. This she does by seizing each 

 one, near its base, between her mandibles, and with a sort of milk- 

 ing motion crowds the pollen out of the terminal pores ; mean- 

 while, by the movements of her feet, the larger stamen is repeat- 

 edly sprung backwards, and as often throws a cloud of pollen on 

 one side of her body ; this in a right-handed flower. When she 

 passes to a left-handed flower, which, as was explained above, is 

 very likely not to be on the same plant, the pollen is carried 

 directly to the pistil of that flower, and so on. We have here, 



