70 COMPENDIUM OF GENERAL BOTANY. 



carried on some researches in which lie demonstrated the presence 

 of 'such perfect mechanical structures among plants. 



Localized Function of Mechanical Cells. Phytotomy reveals 

 numerous instances of the appearance of mechanical cells and cell- 

 complexes which have nothing to do with the flexibility and tractive 

 resistance of organs. The general physiology of tissues in con- 

 junction with mechanics will give the desired explanation of 

 their existence. They evidently serve as a protection to the ele- 

 ments which conduct food substances. The layers of mechanical 

 cells which are frequently found closely associated with the deli- 

 cate tissues which conduct albumen and other substances ("lep- 

 tome-bundles ") are essentially protective in function. Let this 

 explanation suffice for the present. We will again refer to this 

 subject in the discussion of the protective sheath (endoderm, inner 

 derm is). 



IY. THE FUNCTION OF THE CONDUCTING SYSTEM. 



A careful study of the few figures illustrating the mechanical 

 tissue-system will show that the description of the anatomical struc- 

 ture of the stem, root, and leaves would be imperfect if only refer- 

 ence were made to the mechanical tissues involved. We must also 

 discuss the conducting tissue-system. 



We shall at the same time treat of the anatomy of the vascular 

 system and of the mechanical system, showing the respective arrange- 

 ments of the two in the great plant-groups. We shall study the 

 more important organs in which they occur. 



Consideration of the Conducting System in Itself and in its 

 Relation to the Mechanical System. 



(a) The Various Cell-forms. 



NAGELI,* in his researches in plant anatomy, introduced names 

 for plant-tissues which, according to our present knowledge of the 

 subject, have become in part useless. The writer intends to give a 

 lucid presentation of the subject according to the present status 



Beitrage zur wissenschaftlichen Botanik, 1858. 



