

46 ‘ FLOWERING PLANTS 
instance of meristematic cells. These hairs are purple, and 
: offer a striking contrast to 
the yellow anthers. Under 
the microscope a hair 1s seen 
to consist of several cells, each 
showing a. cell-wall, proto- 
plasm with nucleus, and 
vacuoles filled with cell-sap. 
The cell-sap, which is purple, 
saturates the whole cell, and 
if it is a warm day, or if the 
slide is gently warmed, the 
streaming movement in the 
strands of protoplasm may 
be seen. They gradually 
change their shape, growing 
wider in one place and nar- 
rower in another. Groups 
of meristematic cells capable 
of growth and of divid- 
— ing to form new cells are 
Fic. 11.—Harrs, or Trapes- — found at all growing points, 
CANTIA. . 
p, protoplasm ; 7, nucleus with where they contribute to 
threads ; ¢.w, cell-wall. growth in length, as at the 
apex of the root and stem. 
Meristematic cells also occur where growth in thickness, as in 
stems, is taking place; such cells form the tissue known as 
cambium. 

Pieascner Loe formation of the: permanent tissues of a 
Permanent flowering plant is due to the changes that take 
Tueeee: plac ve 
(i.) In the shape of a cell; 
(ii.) In the thickness of the cell-wall and its chemical com- 
position ; | ; : 
(iii.) In the unions of cells with each other. 
If the cells of a tissue remain about the same width in all 
directions, the tissue is called parenchyma. ‘This tissue forms 

Promes O 
