40 LOUIS AGASSIZ. 



a part of the most elementary instruction in 

 botany. 1 



" 1. Where is the first diverging point of 

 the stems and roots in plants, that is to say, 

 the first geniculurn ? 



" 2. How do you explain the origin of those 

 leaves on the stem which, not arising from 

 distinct geniculi, are placed spirally or scat- 

 tered around the stem ? 



"3. Why do some plants, especially trees 

 (contrary to the ordinary course of develop- 

 ment in plants), blossom before they have put 

 forth leaves? (Elm-trees, willow-trees, and 

 fruit-trees.) 



"4. In what succession does the develop- 

 ment of the organs of the flower take place ? 

 and their formation in the bud? (Com- 

 pare Campanula, Papaver.) 



" 5. What are the leaves of the Spergula ? 



" 6. What are the tufted leaves of various 

 pine-trees ? (Pinus sylvestris, Strobus, Larix, 

 etc.) . . . 



" 18. What is individuality in plants ? " 



The next letter contains Agassiz's answer to 



1 Botany owes to Alexander Braun and Karl Schimper the 

 discovery of this law, by which leaves, however crowded, are 

 so arranged around the stem as to divide the space with 

 mathematical precision, thus giving to each leaf its fair share 

 of room for growth. 



