MERISTEM, AND PARENCHYMA 29 



less differentiated or more generalized tissues of the lower 

 plants will not be considered. 



39. Meristem. This is the form of tissue from which 

 ultimately all the other kinds arise. It is often spoken 

 of as rudimentary tissue from this fact. It consists of 

 small, usually rapidly dividing cells (at least during the 

 growing season), some of which usually continue as 

 meristem, while others by enlarging and ceasing their 

 active division and by other modifications become other 

 kinds of tissues. Meristem is present in those parts of 

 the plant where new cells are being formed, i.e. in young 

 buds, at the apex of growing stems and roots, in the 

 developing seeds, etc. Meristem cells are usually small 

 and very thin-walled, and filled with cytoplasm, and 

 with a nucleus which is large in proportion to the size of 

 the cell and mostly central in location. 

 The vacuoles are small or entirely want- 

 ing. At the growing points of stems and 

 roots the cells are usually nearly cubical, 

 in other locations (e.g. cambium) they 

 may be elongated. If the plant be one „ „ ,, . 



•' ° '^ _ FiQ. 9. — Meristem 



with plastids they are present in meri- t'^aue. 



stem cells often as a single, very small, hardly distin- 

 guishable body. Some botanists, however, are of the 

 opinion that plastids are newly formed in the tissues 

 developed from the meristem. 



40. Parenchyma. This is the chief vegetative tissue 

 of the higher plants and makes up much the larger part 

 of the living portions of the plant. It is the main nutri- 

 tive, storage and reproductive tissue. Its cells are 

 much larger than those of meristem, from which it is 

 directly derived, but they preserve in general much the 

 same shape, i.e. they are rounded or polyhedral and usually 

 not much elongated. The cell walls are thicker than 



