148 HETEEOSTYLBD TEIMORPHIC PLANTS. Chap. IV. 



capsules) was accidentally left during several days 

 pressing against the net, and bees were seen inserting 

 their proboscides through the meshes, and in conse- 

 quence numerous capsules were formed on this one 

 small branch. From these several facts it follows that 

 insects will generally carry the pollen of each form from 

 the stamens to the pistil of corresponding length ; and 

 we shall presently see the importance of this adapta- 

 tion. It must not, however, be supposed that the bees 

 do not get more or less dusted all over with the several 

 kinds of pollen ; for this could be seen to occur with 

 the green pollen from the longest stamens. Moreover 

 a case will presently be given of a long-styled plant 

 producing an abundance of capsules, though grow- 

 ing quite by itself, and the flowers must have been 

 fertilised by their own two kinds of pollen; but 

 these capsules contained a very poor average of seed. 

 Hence insects, and chiefly bees, act both as general 

 carriers of pollen, and as special carriers of the right 

 sort. 



Wirtgen remarks* on the variability of this plant in 

 the branching of the stem, in the length of the bracteae, 

 size of the petals, and in several other characters. The 

 plants which grew in my garden had their leaves, 

 which differed much in shape, arranged oppositely, 

 alternately, or in whorls of three. In this latter case 

 the stems were hexagonal ; those of the other plants 

 being quadrangular. But we are concerned chiefly, 

 with the reproductive organs : the upward bending of 

 the pistil is variable, and especially in the short-styled 

 form, in which it is sometimes straight, sometimes 

 slightly curved, but generally bent at right angles. 

 The stigma of the long-styled pistil frequently has 



* ' Verhand. des naturhiot. Vereins, fur Pr. Ehoinl.' 5. Jalirgang 

 1848, pp. 11, 13. 



