88 LETTER II. 



%iire something resembling a saucer ; their veins are 

 unusually prominent, and give the petals a streaked 

 or pencilled appearance. 



We did not see any veins in the petals of the 

 Crowfoots, or the Poppies, or the Umbelliferous 

 plants, and yet we might have found them if we had 

 paid attention, for veins are as regularly found in 

 petals as in leaves, and, what is very curious, they 

 have the same structure, except that they are usually 

 composed of air-vessels only. The tough and flexible 

 tubes, or water-pipes, which you find surrounding the 

 air-vessels in the veins of leaves (p. 12.), are in those 

 organs indispensable for the protection of the air-ves- 

 sels, and for giving strength to the leaf, during the 

 many months which it has to exist ; but all this won- 

 derful provision against injury, would be thrown away 

 in the petals, which never live beyond a few days, 

 sometimes only a few hours ; and would be prejudicial 

 to that delicate and transparent appearance in them 

 which we so much admire. Nature, therefore, who 

 creates nothing in vain, has generally formed petals 

 with veins composed of air-vessels only ; and hence the 

 extreme delicacy of the fragile corolla. The petals of 

 the Geranium are so well adapted to shew you this 

 arrangement, and you must be so curious to witness 

 the way in which the secret workings of vegetation 

 take place, that I am sure you will thank me for 

 teaching you how you can best view the structure. 

 For this purpose place the petal of a Geranium 

 upon a piece of perfectly smooth and flat glass, such 

 as is usually furnished for the transparent stage of a 



