72 Mr. Howard's Account of a Mkrofcopkal Inveji'igation 



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

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

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

 air muft have appeared. I therefore conclude them perfedtly folid 

 in the dry ftate. 



I think it poflible that the profecution of thefe inquiries by 

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

 fubjeft of vegetable reproduction ; may teach us why the anther is 

 almofl: 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 w^hich the ftigma is fur- 

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

 nedfary. 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 furnifli matter for fpeculation; but I 

 decline this, believing that experiment and careful obfervation muft 

 always precede found theory. 



Reflecting 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 ftrufture the 

 fame. Starch confifts of homogeneous grains or capfules fhaped 

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

 tranfparency, and of returning to their original ftate on parting with 

 it. They are alfo difperfed, with more or lefs of motion, in fpirit; but 

 in this particular different 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 great abundance, mixed with fibrous matter. Other kinds 

 of grain afforded the fame refult, with a difference in the form of 



the 



