PLATE XXIV. 



Fig. 262^. Another section through the same prothallium as that shown in 262</. 

 Altogether there are more than twenty archegonia formed in the upper 

 part of this prothallium. X 75- 



263. Archegonia formed not only at the top but along the sides of the en- 

 dosperm. Reconstructed from several sections. Seven of the arche- 

 gonia are visible in a single section. X 31- Pinks montana unciimta. 

 June 10, i8q8. 



264. Linear arrangement of archegonia through the center of the prothal- 

 lium. All of these archegonia are connected with the exterior by a 

 passage above the neck-cells, which does not show in this view, but in 

 the lower ones it leads to the side of the prothallium, rather than to 

 the top. X 31' Pinus atistriaca. June 17, 1898. 



261;. A little archegonium " budding" from a sheath cell of a larger arche- 

 gonium. X 53- Pimis rest'nosa. June 15, 1898. 



266. A smaller archegonium at the base of a larger one and opening into 

 it. The smaller one has no neck-cells and the nucleus of its cen- 

 tral cell has evidently been derived from one of the sheath-cells of the 

 upper archegonium. X3i- Pinus rigida. June 13, 1898. 



267. The same as fig. 266 except that the central cell of the lower archego- 

 nium has divided and the egg has reached maturity, while the nucleus 

 of the central cell of the smaller upper archegonium has not divided. 

 X 46- Pinus resinosa. June 24, 1898. 



268. The largest ventral canal-nucleus observed in Pinus Strobus. There is 

 no wall present cutting off a ventral canal-cell, but the nucleus is free 

 in the cytoplasm of the q%^. X 3i- June 14, 1899. 



269. An archegonium showing the only nucleus of such a large size ob- 

 served in any species for the ventral canal-nucleus. X 46- Pinus 

 austriaca. June 2, 1898. 



270. Fragmentation of the egg-nucleus. X 4'''- Pinus Strobus. June 15, 

 1899. 



271. A pollen-grain after germination showing an increase in the norninl 

 number of nuclei. X472- Pinus austriaca. May 17, 1S98. 



272. The generative cell and another nucleus, not the stalk-nucleus, just 

 passing into the pollen-tube. X472- Pinus Strobus. May 20, 1898. 



273. The generative cell and another cell passing into the pollen-tube and 

 followed by the stalk-cell. Presumably two generative cells have been 

 formed. X 394- Pinus rigida. May 3, 1898. 



274. An archegonium after fertilization. One of the two segmentation-nu- 

 clei has divided while the other has not. X46. Pinus Strobus. 



271;. An instance in which the greater portion of the upper end of the pro- 

 thallium is separated by a considerable space from the nucellar cap. A 

 pollen-tube not able to cross this space and enter between the neck 

 cells has etfected entrance into the side of an archegonium, and the 

 four segmentation-nuclei have been formed ; the fifth nucleus is evi- 

 dently the smaller sperm-nucleus; the very small nucleus at the 

 top may be the ventral canal-nucleus, but more probably it is the tube- 

 nucleus. X3I- Pinus Strobus. June 15, 1899. 



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