734 Mr. Brown on the Organs and Mode of 



EXPLANATION OF THE PLATES. 



Tab. 34. Asclepias purpurascens. 



Fig. 1. A branch in flower: — natural size. 



2. An expanded flower, of which two of the foliola coronae 



and one of the antherse are removed : — moderately 

 magnified. 



3. A front or inner view of an anthera, to show the extent 



of bursting, particularly with relation to the pollen 

 mass, of which the greater part is included in the non- 

 dehiscent portion : — magnified as fig. 2. 



4. A pollen mass, more highly magnified, separated from 



its gland and arm, and divided transversely, to show 

 its cellular structure (first discovered in Asclepias cu- 

 rassavica in 1805 by Mr. Bauer), with grains of pollen, 

 their granules, and some drops of an oily fluid. 



5. A pollen mass entire, with a small portion of the arm 



adhering to its apex : — magnified as fig. 4. 



6. A transverse section of a pollen mass, still more highly 



magnified, in one of the cells of which is seen the 

 single grain (or inner membrane), also separately ex- 

 hibited to show that it is simple and slightly angular. 



7. The pistillum with pollen masses, that have burst and 



protruded their tubes, applied to the base of the 

 stigma, the glands and their arms being removed. 

 The cords formed by the pollen tubes have passed 

 along the corresponding sides of the conical base of 

 the stigma, and have reached the tops of the styles. 



8. A longitudinal section (more highly magnified) of the 



conical base of the Stigma with the two styles, to 

 show more distinctly the course of the pollen tubes. 



Fig. 9. 



