GENERAL SUMMARY. 313 



course of their development, those of Endogens always 

 remain alternate or spiral, those of Exogens may either 

 remain in their primitive state or take a spiral dis- 

 position (Book ii. Ch. 3). 



20th. The appendicular organs which compose the 

 flowers are, in both classes, disposed in concentric ver- 

 ticils ; the innermost are sometimes spiral (Book iii. 

 Ch. 2). 



21st. The protecting appendicular organs hold a middle 

 station, in form, size, colour, and often also in position, 

 between the two other classes ; and we frequently see 

 them metamorphosed, either into organs decidedly nou- 

 rishing, or more rarely into fructifying ones (Book iii. 

 Ch. 1). 



22d. The appendicular organs are generally composed 

 of a petiole and limb, but one of them may be wanting. 

 The Petiole, which is the bundle of fibres not as yet 

 disunited, has its fibres longitudinal ; the Limb, which 

 is the part formed by the expansion of the fibres, has 

 them more or less diverging. These fibres of the limb, 

 or Nerves of leaves, are generally curved in Endogens, 

 and separate at angles more or less acute in Exogens 

 (Book ii. Ch. 3). 



23d. The nerves of curvi-nerved leaves converge 

 towards the apex, or diverge from a middle bundle. 

 Those of anguli-nerved ones arc pinnate, palmate, or 

 pedate ; but the portions of the limb of the three last 

 classes are penni-nerved, so that this form seems essential 

 to the leaves of Dicotyledons (Book ii. Ch. 3). 



24th. The leaves of Dicotyledons are the only ones 

 which have been seen, either composed of joints or 

 leaflets, or furnished with lateral stipules. 



25th. Germs, or the undeveloped rudiments of new 

 individuals, appear able to arise from all parts of the 

 surface; but there are certain points where they are 



