350 STERILE STAMENS. POLLEN. [BOOK i. 



we are unacquainted, some of the stamens are developed 

 imperfectly, without the anther and pollen. In such cases 

 they are called sterile stamens (parastemones Link), and are 

 frequently only to be recognised by the position they bear 

 with respect to the other parts of the flower. Botanists con- 

 sider every appendage, or process, or organ, which forms part 

 of the same series of organs as the true stamens, or which 

 originates between them and the pistil, as stamens, or as 

 belonging to what Roper calls the andrceceum, namely, to the 

 male system ; and every thing on the outside of the fertile 

 stamens is in like manner often referred to modifications of 

 petals, a remarkable instance of which is exhibited by Passi- 

 flora. There is, however, no certain rule by which it can be 

 determined whether such bodies belong to the stamens or 

 petals. 



The appearances assumed by these sterile stamens are 

 often exceedingly curious, and generally veiy unlike those of 

 the fertile stamens ; thus in Canna they are exactly like the 

 petals ; in Hamamelis they are oblong fleshy bodies, alterna- 

 ting with the fertile stamens ; in Pentapetes they are filiform,, 

 and placed between every three fertile stamens ; in Ginger- 

 worts (Zingiberacese) they are minute gland-like corpuscles, 

 a very common form (Plate IV. fig. 10. c.) ; in Brodiasa they 

 are bifid petaloid scales ; and in Asclepiads they undergo yet 

 more remarkable transformations. Dunal calls these sterile 

 stamens lepals (lepald) ; a term which has not yet been 

 adopted. 



9. Of the Pollen. 



The pollen is the pulverulent substance which fills the 

 cells of the anther. It consists of extremely minute grains, 

 varying in size, and inclosing a fluid containing molecular 

 matter. The pollen-grains are often called granules. 



It appears to consist of wax, forming a portion of its shell, 

 of globules of oil, and of starch. Dr. H. Giraud has 

 mentioned the existence of potassa in the pollen of Antir- 

 rhinum majus ; and of raphides, consisting of phosphate of 

 lime, mixed up with the pollen of Tradescantia virginica, and 



