498 MANUAL OF NATURAL HISTORY. 



trorse ; ovaries 0, sessile ; ovules solitary (?) ; 

 styles subulate, or thickened at the apex. 

 Found in Brazilian woods. 



ENDOGENS. 



What is commonly known as the endogenous 

 type of structure characterizes a large assemblage of 

 flowering-plants, forming the class we are now to 

 consider. In importance and extent it approaches 

 the Exogens, and its geographical distribution is 

 quite as varied and general. The most obvious dis- 

 tinctive mark of this division is found in the struc- 

 ture of the stem, new matter being developed in the 

 interior, though, taken in a wide sense, this does 

 not strictly apply. If a cross section be made of an 

 endogenous stem, it will present an irregular, dotted 

 surface, the dots being more numerous towards the 

 circumference, where the wood is also hardest : if 

 cut again vertically, numerous strings or bundles of 

 woody fibres will be seen apparently springing from 

 the centre, and proceeding in a curved direction to- 

 wards the circumference. But the more accurate 

 researches of Schleiden shew that all plants pos- 

 sessing a stem are, to a certain extent, endogenous, 

 and that the true and essential distinction between 

 the monocotyledonous and dicotyledonous classes, 

 consists in the mode and degree of development of 

 the woody or fibro-vascular bundles. In the latter, 



