1912J PACE—PARNASSIA 329 



Fig. 80. — Same: a diagram of an entire ovule with two-nucleate sac; 

 very compact tissue throughout the entire ovule. 



Fig. 81. — S. cordifolia: egg apparatus. 



Fig. 82. — Diagram of the same sac, showing one antipodal and the polars 

 already fused near the base of the sac. 



Fig. 83. — S. crassifolia: embryo and two endosperm nuclei. 



Heuchera brixoides 



Fig. 84. — Part of ovule showing two mother cells which are not exactly 

 parallel and overlap slightly. 



Fig. 85. — Mother cell after synapsis and deep in nucellar tissue. 



Fig. 86. — Mature embryo sac; filiform apparatus and notch well developed 



in the synergids. 



Drosera rotundifolia 



Fig. 87.— Mother cell. 

 Fig. 88. — Mother cell with two hypodermal cells above. 

 Fig. 89. — At least two sporogenous cells, one of which has passed the 

 synapsis stage. 



Fig. 90. — Megaspores developed from a mother cell like that in fig. 87; 

 the fourth megaspore has begun to develop the embryo sac, the other three are 

 almost completely disorganized. 



Fig. 91. — Similar megaspores, but developed from a mother cell like that 

 in fig. 88. 



Fig. 92. — An ovule with two-nucleate embryo sac; large air spaces and 



much spongy tissue in the lower part of the ovule; nucellar tissue with very 



small cells in center and very large ones next to the integument except just over 

 the sac. 



Fig. 93. — The third division in the embryo sac; in the upper nucleus the 

 10 chromosomes may be counted; the small nucellar cells just over the sac and 

 the very large ones toward the base and the small ones in the center of the 

 nucellus below the sac give the Drosera nucellus a very unusual appearance. 



Fig. 94. 



synergids 



and a somewhat dome-shaped filiform apparatus ; the polars have already fused . 

 Fig. 95. — An embryo sac with pollen tube passing around the filiform 

 apparatus and apparently emptying into the synergid; probably the sex nuclei 

 have already fused, but the mass is so indistinct one cannot be sure of the 

 contents of the synergid region. 



Fig. 96. — One synergid shows still a trace of the nucleus and the filiform 

 apparatus; the other synergid shows the notch and above a bit of the pollen 

 tube; in the lower part are two nuclei, probably the synergid nucleus and tube 

 nucleus; the sex nuclei have fused and the endosperm nucleus is in mitosis. 



