48 



PLANTS AND SUNLIGHT 



cally above the first. This is true, 

 no matter which bud is selected as 

 the starting point. Draw a thread 

 around the stem until the two buds 

 are joined. Set a pin at each bud. 

 Observe that two buds are passed 

 (not counting the last) and that 

 the thread makes one circuit of 

 the stem. Representing the num- 

 ber of buds by a denominator, 

 and the number of circuits bj' a 

 numerator, we have the fraction 

 X, ivhich expresses the part of the 

 circle ivhich lies between any two 

 buds. That is, the buds are one- 

 half of 360 degrees apart, or ISO 

 degrees. Looking endwise at the 

 stem, the leaves are seen to be 2- 

 Note that in the apple 

 shoot (Fig. 81, right), the thread 

 makes two circuits and five buds are passed : two- fifths 

 represents the divergence between the buds. The leaves 

 are 5-ranked. 



I. A miiiii I ' ' <' ^niit 



the leiives hung four weeks 

 longer than on the north side, yovilT-p/I 

 because of more sunlight and idUJieu. 

 perhaps more food. 



78. Rhubarb growTi in the dark. The leaf-blades do not develop. 



