532 ON THE ORGANS AND MODE OP FECUNDATION 



therefore, was to ascertain the structure of the pollen 

 mass. 



^ Although on this subject my earliest observations es- 

 sentially agreed with Mr. Bauer's figures of the mass, which 

 represent it as having a sabdivicled cavity with a grain of 

 pollen in each cell ; yet a further examination had led me to 

 adopt the opinion of Treviranus and Ehrenberg, who de- 

 scribe its cavity as being undivided and filled with distinct 

 grains. 



733] I was confirmed in this opinion on considering the state 

 of the mass after the production of the pollen tubes ; for it 

 appeared very improbable that the cells, unless they were 

 of extreme tenuity, could be either suddenly removed or 

 sufficiently ruptured to admit of the passage of the tubes 

 from its more distant parts to the point or line of dehis- 

 cence. 



The appearance, however, occasionally met with, of 

 lacerated membranes proceeding, as it seemed, from the 



' [In the original impression, printed for distribution in October, 1831, tbe 

 passage from tliis point down to the paragraph on p. 534 commencing " On 

 the 16th of July," stood as follows. This was replaced in the 'Linnean Trans- 

 actions' by tliat which is given in the text. — Edit.] 



" My earliest observations on this subject, made on several species of 

 Asclepias, seemed to prove that the mass is cellular, nearly as Mr. Bauer lias 

 represented it. But on a further examination I was convinced that it can be 

 termed cellular only in the early stages, in consequence of the state of the 

 grains of pollen which then certainly cohere ; while in tlie more advanced, and 

 especially in the mature state, it is' no longer really cellular, the grains being 

 now distinct from each other; sections of the mass, however, whether trans- 

 verse or longitudinal, still exhibit a cellular appearance. 



"These grains, when in this their perfectly developed state, are colourless, 

 nearly round, but slightly and obtusely angular, probably from mutual pressure, 

 much compressed, with an undivided cavity, and no indication of their being 

 composed of four or any other number of united cells. Their membrane is 

 transparent, and has no appearance of being made up of two united coats, and 

 the cavity is fiiled and rendered opaque by spherical granules of nearly uniform 

 size, witii occasionally a few oily particles. lu this state no appearance or 

 indication of the tubes or appendages described by Dr. Khreuberg was found. 



" The general covei'ing of the mass, which is of a deep yellow colour and very 

 distinctly areolated, the meshes being angular, and in size as well as in form 

 nearly corresponding with the included grains, may perhaps be considered as 

 the outermost series of cells, whose laminae are closely applied to each other, 

 as in the epidermis, and their cavity consequently obliterated. They thus form 

 a coat of considerable thickness, necessary for the protection of tlie grains of 

 pollen, in a mass which is destined to be removed from its original place by an 

 insect, and applied by this agent to a distant part of the same or of a different 

 flower." 



