310 
METHODS IN PLANT HISTOLOGY 
For a study of the monocotyl embryo, Iris, and especially 7. pseuda- 
corus, can be recommended. The embryo is straight, and cotyledon, 
stem-tip, and root are clearly differentiated before the endosperm 
Fig. 114.— Capsella bursa pastoris: A, filamentous stage; B, first division of the embryo cell; 
C, octant stage; D, dermatogen has been cut off, except at the tip of the root; E, differentiation 
into periblem and plerome of the root and differentiation of the periblem of the root; F, further 
development of root but stem not yet differentiated into periblem and plerome; G, completion of 
dermatogen of root; H, two layers of root cap have been formed; H\ topography of entire embryo 
at stage shown in H. Only dermatogen and plerome shaded. A-H, X580; H' X75. 
becomes too hard to cut in paraffin. Fix pieces about 3 mm. wide 
cut perpendicular to the face of the cheese-shaped seed. Do not try 
to cut the whole pod. 
