LEAF- ARRANGEMENT. 87 



If a part of them be oppressed ? What if all ? 249. What is a brachiate axis ? How in 

 the Pink ? How in Catalpa ? 250. What are accessory buds ? Adventitious ? Examples. 

 252. What is Vernation ? How may we study it ? Considering each leaf alone, when is 

 it reclined ? Conduplicate ? Plaited ? When circinate 'Convolute 'Involute ? Revo- 

 lute ? How is the vernation in Oak ? Dock ? Birch ? Fern ? etc. 258. Considering 

 loaves combined, when are they obvolute ? Equitant ? Triquitrous ? 259. State the 

 principle of Budding. What are Bulblets ? 



CHAPTER XIX. 



PIIYLLOTAXY, OB LEAF-ARRANGEMENT. 



261. As the position of the leaf upon the stem marks the po- 

 sition of the axillary bud, it follows that the order of the leaf- 

 arrangement will be the order of the branches also. The care- 

 ful investigation of this subject has developed a science of 

 unexpected exactness and beauty, called phyllotaxy (<poXXov, a 

 leaf, T|/, order.) 



201 Ladies' -slipper (leaves alternate); 292, Synamlra granrtiflora (leaves opposite); 294, Medeola Vir- 

 ginica (leaves verticillate); 293, Larix Americana (leaves fasciculate). 



262. In regard to position, leaves are radical when they grow 

 out of the stem at or beneath the surface of the ground, so as to 

 appear to grow from the roots ; caitline, when they grow from 

 the stem ; and ramial (ramus, a branch), when from the branches. 



