83 



i 



A 



these twin-celled hairs, if the filaments are taken for study 

 while young. The surface is at first smooth, as indicated at a, 

 and not unlike the exterior of ordinary fila- 

 ments and similar plant structures. In slightly 



older stamens it 



is easy to recognize small 



enlargements at certain places, where the sur- 

 face cells meet end to end. Such a minute 



swelling is indicated in side view at d. The U}-!: 



ends of these two cells take on a lateral growth 



/ 

 and soon become bent at right angles to the 



surface 



of th 



e filament. The protoplasmic 



contents of each cell flow into the free, extended portion, and 

 leave the old epidermal part comparatively empty. The nucleus 

 IS plainly visible in the lateral portion, when the hair is not more 

 than half grown. 



These trichomes, therefore, originate by the lateral extension 

 of the ends of two adjoining cells, and they evidently play an 



VA.O" ' ^'-d'-i. 



important part in the movements of the filaments. The addi- 

 tional figures in the engraving show older stages in the develop- 

 ment of the hair. At c and d the young outgrowths are rapidly 

 developing, and the protoplasmic contents are quite dense near 

 the tips of the cells. Two mature hairs are shown at e and / 

 the former in side view, while the latter is looking down upon 

 the surface, and indicates the relative lengths of the cells. From 

 tile beginning of the development of the hair, there is an evident 

 common layer over the two specialized cells. This is most appar- 

 ent when the trichome attains full size, that is when about a mil- 

 limeter long and 20 to 25 M broad. The protoplasm was fre- 

 quently found in rapid circulation in the full-grown cells, and 



