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. Bie 
a2 
The vacuoles are small or entirely want- 
ing. At thegrowing points of stems and oot e 
roots the cells are usually nearly cubical, /3é = 
in other locations (e.g. cambium) they 
may be elongated. If the plant be one 
with plastids they are present in meri- tissue. 
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 
