ANATOMY OF TISSUES. 119 
periblem, and plerome. Besides these, in certain instances there 
is an independent, separate meristem named calyptrogen which 
gives rise to the root-cap. Thus there are in the most complex 
roots, four distinct primary meristems. Others lack the calyp- 
p 
Fie. 51. 
Longitudinal section through root tip of Zea Mais. W root-cap; i younger part. 2z cells 
loosening from cap. s point of vegetation. o epidermis. p’periblem. pplerom. d 
dermatogen bounded on the under side by the calyptrogen. x 150. —( Wiesner.) 
trogen, the cap tissue there being derived from what is termed 
the reciprocal division of some of the other meristems. That 
is, the meristematic cells give off new cells in two directions, 
some outward, forming the cap, others inward which are added 
to the long axis of the root. The farther consideration of this 
subject belongs to a more advanced course in anatomy. 
