Organs and Fertilization in Picea excelsa . 357 
Belajeff, and Coulters drawings 1 leads me to think that they 
too saw the entire stalk-cell in the pollen-tube ; it was, how- 
ever, interpreted by them as a mere nucleus. 
The tube-nucleus, which is often somewhat irregular in 
outline and has a prominent nucleolus, is always located near 
the tip of the pollen-tube (Figs. 10-16, 18-21). This nucleus 
seems to play an important part in the elongation of the 
pollen-tube ; it has been observed in Ginkgo (Hirase ’ 98 ) and 
Cycads (Ikeno ’ 98 , Webber ’01) that when the tip of the 
pollen-tube ceases to grow and the other end of the tube 
begins to elongate, a little while before fertilization, the tube- 
nucleus migrates to this new growing portion. 
The starch-grains, which can usually be observed in the 
mature pollen-grain, increase much in size and amount after 
the formation of the pollen-tube. Very often these grains 
have deeply staining portions, which I have not sketched in 
my drawings, in their centres. They are probably the cracks 
or spaces left by the dissolution of some of the starch in the 
centre of the grain. The starch-grains also appear in the full- 
grown stalk-cell shortly before its passing into the pollen-tube ; 
after the cell has entered the tube starch is no longer visible 
in it (Fig. 11). The stalk-cell with starch-grains was also 
observed in Zamia by Webber (’01). 
Early Development of the Archegonium. 
The archegonium usually develops from a superficial cell 
at the apex of the female prothallium. When the prothallium 
reaches a certain size, some of the cells in the uppermost 
layer cease to divide, but continue to grow, so that they are 
distinguished from the adjacent cells by their larger size and 
larger nuclei. These are the initial cells of the archegonia 
(Figs. 23, 24). While this archegonial initial is only a few 
times as large as the adjacent cells it divides, giving rise to 
a small upper cell, the mother-cell of the neck, and a large 
lower cell, the central cell of the archegonium (Figs. 25, 2 6). 
1 Strasburger ’ 92 , Figs. 43, 44 ; Belajeff ’ 93 , Fig. 16 ; Coulter ’ 97 , Fig. 5. 
