IrritahUl/y of the Pollen ef Plants. .-ji 



any expence had been Incurred. In thefe, and in numberlefs other inftances, it would 

 have been incomparably more advantageous to have rejeded the material upon the firft 

 trial, rather tha- have proceeded to the very expenfive procefs of manufaauring the article, 

 and then finding it of no value. By this fimple expedient I have feen bars of fleel as full of 

 veins and irregularities as wood, and have been enabled to feleft the bell and moll uniform 

 pieces for works of the greateft delicacy ; whereas, before I thought of this mode of trial, 

 I have very often had the mortification to fail in the laft ftage of experimental pioceifes,' 

 upon which much cod and labour had been bellowed. 



VIII. 



On the In-itahilUy of the Pollen of Plants. With an Aecount of a Compoftkn for clofng 

 Wide-mouthed Veffels. 



To Mr. Nicholson, Editor of the Phikfiphical Journal. 



-Tl FE W fummers ago a friend of mine chanced to make a curious difcovery relative to 

 die irritability of the pollen or fecundating duft of plants ; which, as I know not that it has 

 yet met the eye of the public, you are at liberty, if thought fufficiently interefting, to com- 

 municate through the channel of your Journal. 



Whilft making obfervations with one of Adams's compound microfcopes on the figure 

 of the particles of pollen coUeaed from diiferent plants, he applied a drop of water to a 

 fmall group (which was placed on the glafs plate of the Rage), in order to increafe the 

 bulk ; and, by that means, more accurately determine the figure of the particles. Happen. 

 ing, at the fame time, to have a fmall phial of fpirits of wine at hand, he next tried a drop 

 of that liquid to freQi pollen, when he was agreeably furprifed with feeing it produce a 

 quick gyration, as well as a darting of the particles backward and forward in the drop • 

 this motion continued for a few minutes, and then gradually fubfided ; the particles un- 

 ravelling into a continuous filmy thread, and at other times appearing to burft and emit 

 a multitude of particles *■ infinitely fmaller, and which conglomerated together,' Icwne 

 the capfular veiTel empty, or only filled with the fpirit. ' 



The fpeedy evaporation of the fpirit appearing at times to prevent the completion of the 

 phenomenon, he afterwards tried, and with better fuccefs, a little common brandy. The 

 motions, in this cafe, were continued longer, and the appearances were more complete. It 

 will appear that thefe do not proceed from the mere evaporation of the liquid, becaufe thofe 

 particles which have been once faturated, though from fome caufe they may not have burft 

 or unravelled, are Incapable of excitation, at leaft in any fimilar degree, by the application 

 of more fpirit. 



Different kinds of pollen were made ufe of for this experiment ; but that of the " Caflus 

 flagelliformis" was moftly employed, as affording the molt flriking appearance, on account 

 of the magnitude of its particles. 



• At lead it prcfented this appearance at times to my eye ; wliicli, I doubt not, has been the occafion of its 

 oblaininj; from fome botaiiifts the apiiiliatioii of ihc fptrmatic aura of pollen. 



* I avoidi 



