COMPOSITiE 237 



Aster 



The ray flowers in a single row, female ; sometimes 

 absent. We have two species — A. Tripolium, with ray 

 flowers ; A. Linosyris, without. 



A. Tripolium (Sea Aster) is common in salt marshes 

 along our coasts. As in so many shore plants, the 

 plant is glabrous and the leaves are succulent. The 

 ray florets number 20-30, are purplish violet, and 

 female ; the disk florets are yellow, with stamens and 

 pistil. The disk florets are tubular below and bell- 

 shaped above. In the first stage the anther tube pro- 

 jects, and the pollen is pushed out by the brush of the 

 pistil. The lobes of the corolla are horizontal. In the 

 second the anther tube has retired into the cup of the 

 flower, the lobes of the corolla are upright, and the 

 stigmas protrude, exposing the stigmatic surface. 



A. Linosyris has no ligulate ray flowej-s. The life-his- 

 tory of the florets is much the same as in ^. Tripolium. 



Erigeron 



Ray flowers in several rows, female, narrow or almost 

 filiform. Disk fiowers often but few, complete. The 

 pistil of the female flowers is without a terminal brush, 

 which would be useless in the absence of pollen. We 

 have two species — E. acre, which is annual or biennial, 

 and -E. alpinum, which is perennial. E. canadense, 

 which has thoroughly established itself, difi'ers from the 

 other two in having the outer florets filiform. 



E. alpinum is gynomoncecious. According to H. 

 Miiller there are two forms of female flowers — in the 

 one the ray is conspicuous, in the other it is absent ; so 

 that there are three kinds of flowers in each head. The 

 complete flowers also produce honey. According to 

 Kerner the stigmas of the female flowers are mature 

 some days before the pollen of the complete flowers in 

 the same head. 



E. acris (Fleabane). — The life-history of the flower 

 resembles that of E. alpinum. 



