Mr. Hassall on the Structure of the Pollen Chmnule. 93 



On the Continent entire Avorks have been pubhshed upon 

 the pollen, accompanied by numerous figures : I allude parti- 

 cularly to Purkinje's work, ' De Cellulis Antherarum fibrosis,' 

 &c. ; to that by Fritzsche ; and to a memoir by Mohl in the 

 * Annales des Sciences Naturelles,' all of which have appeared 

 within, I believe, the last ten years. 



With the opinions contained in these w^orks I am only 

 acquainted in so far as they are given us by Lindley, as I 

 wished, before consulting them, to form a separate and in- 

 dependent opinion, so that all 1 shall advance in this paper 

 is to be regarded only as the result of my own investi- 

 gations, and rests upon my own responsibility. It is my 

 intention to publish, from time to time, a series of papers 

 upon the subject of the Pollen, in some of w hich I shall give 

 the opinions of the authors to whom I have referred more 

 at length ; thus mynot doing so at present will be of but little 

 consequence. 



Although I do not anticipate that the results of this inquiry 

 will be very considerable in a practical point of view, I yet 

 feel that I ought not to be deterred from the pursuit because 

 I am not at once able to perceive any great utility attached to 

 it ; the subject is one of much interest in itself j and may ul- 

 timately lead to more than is at present looked for. 



I could have wished that an investigation of such nicety 

 and extent had fallen to the lot of some individual of greater 

 capability and experience in microscopical research ; but as 

 this is merely an essay, and as I shall advance nothing but 

 what I have fully made out, I trust that the inquiry will not 

 suffer by reason of my comparative inefficiency for the task 

 I have undertaken. 



Conceiving then that the want of an accurate knowledge of 

 the form and structure of the pollen grain in the different ge- 

 nera of plants constituted a desideratum in botanical science, 

 I commenced the investigations the results of which I am 

 about to detail early in the spring of last year, continued them 

 throughout the greater part of the summer, and the small 

 amount of time which I have this seast^n been able to spare 

 from professional pursuits has been employed in correcting 

 and confirming the conclusions previously arrived at. 



I shall divide my subject into three heads. Under the first 

 head, the pollen generally will be spoken of; under the se- 

 cond, the individual peculiarities of the pollen granule will be 

 noticed ; and lastly, the pollen will be considered with a view 

 to ascertain w hether it can be rendered available as a means 

 of classification. 



First then, of the pollen generally : 



