320 BOTANICAL GAZETTE [OCTOBER 



The mature sac (fig. 94) has the usual appearance. The syner- 

 gids have a well developed filiform apparatus and notch. The 

 former is somewhat more dome-shaped than in Parnassia, where it 

 is pointed. The synergids are also rather long, reaching almost as 

 far as the lower edge of the egg. The polar nuclei have already fused. 

 Fertilization apparently takes place as in Parnassia. The pollen 

 tube passes around the filiform apparatus and seems to enter one 

 synergid (fig. 95). Here probably the fusion of the sex nuclei has 

 already taken place, as only one nucleus can be distinguished in the 

 lower part of the dark synergid and probably another in the still 

 darker mass higher up. Fig. 96 is clearer in this respect. A small 

 bit of the pollen tube can be seen in contact with the filiform 

 apparatus. This synergid is somewhat darkly stained, but still all 

 structures are distinct, the notch and two nuclei; these are the 

 synergid nucleus and the tube nucleus from the pollen tube. The 

 other synergid is very pale and all the lower part has disappeared. 

 The fertilized egg has not yet divided, but the primary endosperm 

 nucleus is in mitosis; the spindle fibers are forming. So far as 

 examined, this nucleus always divides before the fertilized egg in 

 Drosera. Many cases were seen with two endosperm nuclei and . 



the egg still undivided. 



Discussion 



Three other genera of the Saxifragaceae have been more or less 

 completely worked out. Eichinger (7) figures an ovule of Chrysos- 

 plenium with mature embryo sac that has three layers of nucellar 

 tissue above the sac. In Astilbe Webb (25) reports several arche- 

 sporial cells and one or even two or three megaspore mother cells 

 beginning to divide. The embryo sac is deep in the nucellar tissue, 

 but no filiform apparatus is shown. The embryo has a suspensor ot 

 several cells. Fischer (9) in Ribes aureum shows ovule development 

 similar to that olSaxifraga, except that the filiform apparatus is not 

 shown. Tischler (24) in a mature embryo sac of Ribes sangu- 

 nineum shows pointed synergids but no filiform apparatus or notch. 

 These cases may indicate that these three genera do not have the 

 filiform apparatus and notch. But it is also possible that the 

 material studied was not at the right age to show these best, or was 

 not cut to the best advantage for these particular structures. 



