FECUNDATION IN PLANTS. 
CHAPTER I.—INTRODUCTION. 
The processes of nuclear division and cell-formation are so closely 
associated with sexual cells and their development that an adequate 
understanding of these cells is impossible without a definite and 
thorough knowledge of the processes involved in their development. 
Our interpretations of the significance of the sexual process and the 
phenomena of heredity in all organisms will be more lasting and help- 
ful as scientific knowledge if these interpretations or doctrines are 
based upon a well-connected phylogenetic series of the most funda- 
mental facts. Perhaps no other field of research has been more 
helpful during the past quarter of a century in enabling the biologist 
to gain a deeper and more far-reaching knowledge of the physical 
basis of heredity than the study of mitosis, especially in reproductive 
cells. The division of the nucleus naturally suggests the division of 
the cell, or the process by which new cells are formed from a mother- 
cell, and the study of cell-formation in very recent years, especially 
among the lower plants, has not only wrought almost a revolution 
in our knowledge of the processes here involved, but has also furnished 
new criteria for determining relationships and probable lines of descent. 
It is deemed necessary, therefore, to introduce the subject of sexual 
reproduction in plants by a brief presentation of the typical processes 
of nuclear and cell-division in both the lower and higher forms. In 
doing so these processes will be described in a few of those forms 
‘which have been subjected to a critical study by means of the most 
improved methods and instruments. The processes described will be 
confined largely, though not exclusively, to spore mother-cells. 
The division of the nucleus and of the cell presents generally three 
processes, the development of the karyokinetic spindle, the behavior 
of the chromatin, and the formation of the cell-plate or new plasma 
membrane. This division is made merely for the sake of convenience, 
as it is not implied that three distinct or separate processes are 
necessarily involved, although the development of the plasma mem- 
brane in many cases has apparently little or no connection with the 
