PLATE XIX. 



Pinus Strobus unless otherwise indicated. 



FIG. 206, a-g. Portions of the reticulum from different mature egg-nuclei, 

 showing some of the variations which may occur in the structure of 

 this nucleus. X 1050. 



207. Division of the central cell, showing also the lower portion of a pollen- 

 tube which has already reached the endosperm. In this instance a 

 very short time would have elapsed between the division of the central 

 cell and fertilization. X 2 9 Pinus montana uncinata. 



208. The primary nucleolus from a mature egg-nucleus with secondary 

 nucleoli clustered about it and evidently formed by it. The primary 

 nucleolus has a great affinity for stains at this time. X IO 5- 



209. The primary nucleolus of a mature egg-nucleus. This nucleolus 

 shows a weak reaction towards dyes, and apparently has an outer, 

 limiting membrane. X IO 5 



210. The framework of a primary nucleolus from a mature egg-nucleus. 

 This nucleolus has remained of a light greenish-yellow color after 

 treatment with Flemming's triple stain. X IO 5- 



211. The upper part of an archegonium showing cavity, the receptive 

 vacuole, formed in the cytoplasm just prior to fertilization. X I 4- 



212. The upper part of an archegonium just after the entrance into the egg 

 of the elements from the pollen-tube. X 140. 



213. A slightly later stage. The cytoplasm of the sperm-cell has already 

 fused with the cytoplasm of the egg. X I 4- 



214. An entire archegonium showing the sexual nuclei in contact, and, 

 above them, the various elements which have come into the egg from 

 the pollen-tube. X 62. June 21, 1898. 



215. The upper part of an archegonium in the same stage as the above. 



X HO- 



(192) 



