72 Mr, Howard's Account of a MkrofcQpkal Invejllgation 



have feen a fingle bubble of air efcape from the grains of pollen ia 

 the whole courfe of my obfervations. As their texture was in many 

 cafes quite deftroyed, if it had been porous, as that of dry wood, &c, 

 air mud: have appeared. I therefore conclude them perfectly folid 

 in the dry ftate. 



I think it poiTible that the profecution of thefe inquiries by 

 means of the microfcope, may throw fome light on the obfcure 

 fubje6l of vegetable reprodudlion ; may teach us why the anther is 

 almoft always expofed to the air for fome time previous to the dif- 

 charge of the pollen, and this even in aquatic plants ; as alfo what 

 is the office of that faccharine liquor with which the fligma is fur- 

 nifhed, and of which fuch a ftore is fometimes provided in the 

 ' nectary. The very manner in which the impregnation takes place 

 may poffibly be learned by attentive obfervation. 



The fimilarity of the unfolded pollen of No. 4. to the form of the 

 plant it comes from, might furniih matter for fpeculation ; but I 

 decline this, believing that experiment and careful obfervation mufl 

 always precede found theory. 



Reflecfing on fome of the properties of pollen in which it 

 bears a refemblance to ftarch, I was led to examine that alfo in a 

 fimilar manner, and was not difappointed to find its flru(51ure the 

 fame. Starch con fills of homogeneous grains or capful es fhaped 

 like No. 3. capable of imbibing water with increafe of bulk and 

 tranfparency, and of returning to their original fl:ate on parting with 

 it. They are alio difpeifcd, with more or Icfs of m.otion, in fpirit; but 

 in this particular difierent fpecimens were found to vary, which 

 may be attributed to difference in age or foundnefs. If a little wheat 

 flour be -mixed with water and fpread on the glafs, thefe grains ap- 

 pear in grtcit abunduncc, mixed with fibrous matter. Other kinds 

 or grain affbidcd the Hime refult, with a difference in the form of 



the 



