33 6 



FOURTH GROUP. SEED-PLANTS. 



of the tube. There it divides, as can be seen with especial distinctness in Juniperus 

 virginiana,) and cell-formation takes place round each of the new nuclei by the 

 gathering of protoplasm round them. While the upper one of the two primordial 

 cells does not usually divide again, the lower divides once or twice, and the new cells 

 spread themselves out in one plane at the lower extremity of the tube. The nucleus 

 of the oosphere, which has increased in size and contents, advances towards the middle 



FIG. 262. Juniperus communis. I three archegonia closely side by side cp, two of them having the oosphere 

 fertilised ; d neck-cells, p pollen-tube (July 28). // a similar preparation ; e e the prothallium (endosperm), -v v the 

 pro-embryos. /// lower end of one of the longitudinal cell-rows of a pro-embryo with the rudiment of the embryo e b. 

 IV longitudinal section of the nucellus kk ; e the endosperm, e 1 the portion of the endosperm which has become loose 

 and spongy, p the pollen-tube, cp the archegonia, v suspensors (beginning of August). After Hofmeister. / magn. 

 300, 7F8o times. 



of the oosphere, while the canal-cell becomes disorganised. During fertilisation the 

 small nuclei in the pollen-tube over the archegonia disappear, and their substance 

 must in some way or other pass into the archegonia. A round cell-like body is found 

 in the oospheres of the archegonia in front of the extremity of the pollen-tube, and 

 Strasburger has named it the sperm-nucleus (male pro-nucleus). This object, which 

 must be considered to have passed from the pollen-tube into the oosphere, moves towards 

 the nucleus of the oosphere (female pro-nucleus) and coalesces with it. It follows that 

 in this case also fertilisation consists in the union of the constituents of two cells, for 

 it is plain that there is here not only a coalescence of two nuclei, but a union of the 

 protoplasm of the pollen-tube with the protoplasm of the oosphere. After fertilisation 



