456 BOTANICAL GAZETTE [JUNE 
Although such an explanation of the tapetal layer is impossible 
for many microsporangia, as in Cnicus,? yet its possibility has 
been suggested by Coulter in Ranunculus.3 By gradual changes 
the tapetal layer is clearly differentiated from the spore mother- 
cells until it stains more deeply, has a more homogeneous appear- 
ance, and acquires a tendency to separate from the spore 
_ Stiraca Japonica, 
section through flower with all parts represented and 
apOorlial 
a fl 3 
é. ene ee : SEV oe 
section with the first layer of tapetal cells and two poten- 
° h several cells in the layer might from their 
tapetal or sporogenous (fig. 79). This 
‘the thickening of the tapetum, until it 
food material, homogeneous throughout, oo 
the fe : ae Ranunculus. Bor. Gaz. a5: 73-88. : 
