^SCULUS. 



193 



thence excurrent, giving off numerous straight branches and 

 forming an oval or pyramidal, dense crown of foliage. 



The Leaves are a perfect exemplification of symmetry 

 and order. In arrangement they are in pairs, one leaf oppo- 



FiG. LIT.— ^sculus Hippocastanum. 



3, seed germinating. 



site another,* supported on long slender petioles. At top 

 the petiole divides, as in the Majile, into 7 veins diverging 



* The learner has already observed three modes of leaf -arrangement, viz., the 

 alternate in the Eoseworts, etc., the ojrposite in the Maples, and the rerdcUlate in tlie 

 Loo(?e!<trife. He will now be interei^ted in comparing thoni. In the alternate arrange- 

 ment there i;? only one leaf at each node ; in the ojjposite, there are two, and in the 

 verticillate, 3 or more. The true nature of the alternate may be learned by an experi- 

 ment. Select a .straight, leafy !>hoot or s^tem of an Api)le-trce, Evening Primrose, or 

 any plant with seemingly scattered leaves. Beginning with the lowest leaf, fix a 

 thread to the base of the petiole. Pass then, right or left, to the ne.vt leaf above and 

 do the same ; thence to the next in the same direction, and so on by ail the leaves to 

 the top. The thread will form a regular spiral. Let the same experiment be repeated 

 in a shoot with opposite leaves, and two si)irals running i)arallel with each other will 

 be found ; and in the case of verticillate leaves, as many sjiirals as there arc leaves in 

 each verticil. Hence the course of development in all growing plants is spiral. (See 

 ClassBook, pp. 46-50, on Ph yllotojy .) 

 9 



