734 Some remarks on the development of Pollen. [Nov. 



pointing out clearly the nature of the longitudinal furrows of such 

 common occurrence in the ordinary forms of Pollen. 



In the two other instances which I have selected as demonstrations, 

 the steps are much the same. Care must be taken not to confound 

 the appearance presented by the Pollen of Luffa fcetida at a late 

 period of its development, and which evidently arises from the strong 

 inflection of the outer membrane, with that occasioned by the much 

 earlier dividing process. 



In Hedychium I have been unable to examine the development at 

 a sufficiently early period, but it appears to me the divisions of 

 the original or parent cell form the outer coats of the subsequent 

 grains of Pollen : this is certainly not usually the case. The Pollen 

 of this plant is remarkably simple, for it is neither provided with fur- 

 rows nor apparent pores. 



The inner coat, — for I am disposed to believe that it has one, — ad- 

 heres strongly to the outer, and none of the ordinary means are 

 sufficient to ensure its separation. 



As I have, since a portion of the above was written, received num- 

 bers of the Annales des Sciences Naturelles for March and April 1 835, 

 in which occur extracts of considerable length from the writings of 

 Mr. Hugo Mohl, who has published lately (1834) at full length on 

 this important organ, it may not be amiss here to state the principal 

 results to which this botanist has arrived ; noticing, however, only 

 those which relate to development and structure. 



After pointing out that in by far the greater number of cases, the 

 inner membrane, which contains the fovilla, is enclosed in a second 

 membrane, M. Mohl proceeds to a detailed account of the outer 

 membrane. This is represented as being always finer than the 

 inner, and as generally determining the form of the grain ; and that it is 

 to the liquid secreted by it that the colour and viscosity of the grain 

 is to be attributed. 



The punctuation which frequently exist in this membrane are 

 supposed to be rudimentary cellules ; hence the comparison of this 

 coat to a simple cellule is altogether inexact ; it should be considered 

 as an organ composed of cellules or the rudiment of cellules, and a 

 homogeneous uniting membrane, and hence it should be compared 

 with compound membranes ; such, for instance, as those of the ovule. 



It is only in a small number of plants that this coat presents the 

 form of a perfectly closed, continuous, sphaerical sac ; in most cases it 

 is either furnished with folds or pores, or both. 



Up to the period of M. Mohl's publication nothing whatever was 

 known of the nature, functions, or number of these folds ; most bo- 



