JS BOTANY FOH BEGINNERS. [Ch. X. 



th) tfty in this situation for a length of time ; but as soon as trie 

 whole plant was placed under the receiver, it withered and 

 died. 



228. The upper surface of leaves is usually of a deeper green, 

 and supposed to perform a more important part in respiratioiij 

 than the under surface. The upper surface repels moisture, 

 you may perceive, by examining a cabbage leaf after a showei 

 c heavy dew, that the moisture is collected in drops, but hag 

 n- appearance of being absorbed by the leaf. It has been found 

 ti at the leaves of plants, laid with their upper surface upon wa- 

 tt r, wither almost as soon as if exposed to the air, although the 

 leaves of the same plants, placed with their under surfaces up- 

 on water, retain their freshness for some days. 



229. But few among the vegetable tribes are destitute either 

 of leaves, or green stems, which answer as a substitute. The 

 MonotropO) or Indian pipe, is of a pure white, and looks as if 

 made of wax. Mushrooms are also destitute of any green 

 herbage. It is not known in what manner the deficiency of 

 leaves is made up to these vegetables. 



230. The period in which any species of plant unfolds its 

 leaves, is termed Frondescence. Linnaeus paid much atten- 

 tion to this subject ; he stated as the result of his investigations, 

 that the opening of the leaf-buds of the Birch tree, (Betula,) was 

 the most proper time for the sowing of barley. The Indians oi 

 our country had an opinion, that the best time for planting In- 

 dian corn, was when the leaves of the white oak first made 

 their appearance ; or, according to their expression, are of the 

 size of a squirrel's ears. 



231. One of the most remarkable phenomena of leaves, is 

 their irritability, or power of contraction, upon coming in con- 

 tact with other substances. Compound leaves possess this 

 property in the greatest degree ; as the foieign sensitive plant, 

 and the American sensitive plant: these, if the hand is brought 

 near them, seem agitated as if with fear; but as they are desti- 

 tute of intelligence, we must attribute this phenomenon to some 

 physical cause, perhaps the warmth of the hand, which produces 

 the contractions and dilatations of the leaves. 



232. The effect of tight upon leaves is very apparent, plants 

 being almost uniformly found to present their upper surfaces 



228. In what respects do the upper and under surfaces of leave* 

 d fieri 



2*29. What plants a r e destitute of leaves? 



230. What is meant by the term Fronde.scencel 



231. What is said of the irritability ofleavesl 



23'2 What if said of the effect oJ light upon leaves? 



