264 Cross — Eupatorium ageratoidcs and coelestinum. 



hairs, that sweep the pollen from the anther cylinder, 

 hence called sweeping hairs (Fig. 6 e). Interspersed among 

 the sweeping hairs are occasional goblet-shaped multicellu- 

 lar hairs. Immediately below the sweeping hairs are the 

 stigmatic papillae (Fig. 6 d and d') arranged laterally in 

 groups of three or four {d') covering almost the entire 

 length of the lower third of the style arms. In this species 

 there is a glabrous area at the base of the style arms. The 

 style is slightly swollen at its base, and surrounded by an 

 annular nectar gland g. 



{b) The Pistil of E. coelestinum (Fig. 6) is longer than 

 in ageratoides and is frequently twisted. The stigmatic 

 papillae extend entirely to the bases of the erect style arms 

 which have enlarged club-shaped tips — Fig. 6 e. Hilde- 

 brand * states that in E. cannabinum the stigmatic surfaces 

 remain closely appressed, and that the stigmatic papilla* 

 are not fully developed until after the pollen is matured, 

 shed, and carried away by insects, so that cross pollination 

 is insured. In the dried specimens of E. coelestinum 

 examined, the style arms were slightly separated before 

 they protruded beyond the top of the anther cylinder, but 

 the stigma was not fully developed. In the matured flowers 

 the style stands more erect than in E. ageratoides. In 

 flowers not fully expanded, and with the anther cylinder 

 closed at the top, the style showed a distinct, loop-like cur- 

 vature just above the receptacle (Fig. 6 f). In fully ex- 

 panded flowers the style is quite straight. 



The five anthers cohere to form a hollow cylinder which 

 is rilled with pollen when the corolla begins to expand. In 

 the first stage with its two style arms closely applied to one 

 another, the pistil extends to the base of the anther cylinder 

 and gradually elongates, pushing the pollen before it out 

 of the cylinder by means of the outwardly directed sweep- 

 ing hairs (Fig. 6 e) which cover the upper part of the 

 style arms. When the stigmatic portion, which is smaller 



* " Ueber die Geschlechts-Verhaltnisse bei den Compositen." Verhand 

 der Leo. Carol. Acad. Dresden. Vol. 35 (1869). 



