198 Ferguson . — Development of the Pollen- tube and the 
generative cell. The latter cell passes into the pollen-tube 
before giving rise to the sperm-nuclei. 
Strasburger (’92) showed that BelajefFs observations on the 
development of the pollen-tube in Taxus baccata were in 
general true for the other Gymnosperms. He described the 
mature pollen-grain in Pinus sylvestris , noted that the vegeta- 
tive nucleus passes into the pollen-tube immediately upon 
germination, and remarked that the last formed prothallial 
cell remains in its place in the pollen-grain until the following 
spring, when it divides into the stalk- and the body-cell of the 
antheridium. The division of this cell was not studied, but 
Strasburger thought it took place at about the same time 
as the development of the archegonia. He also stated that 
the lower sperm-cell is the larger, and described each cell 
as being almost entirely filled with its large, coarsely granular 
nucleus. 
Belajeff (’93) worked out the development of the pollen- 
tube in Picea as a type of the Abietineae. He found that 
the generative cell divides while still in the pollen-grain, and 
gives rise to two sperm- cells which he figured as of the 
same size. 
Dixon (’94) traced the history of the pollen-grain and the 
pollen-tube in Pinus sylvestris from the time of pollination 
to fertilization. According to his observations Pinus agrees 
in the main with Picea , as described by Belajeff. In general 
I cannot confirm Dixon’s results, and they will be considered 
more fully in the body of this paper. 
In giving an account of some work done by his students 
on the Gymnosperms, Coulter (’97) reported that the work 
of Dixon ‘was largely confirmed in the minutest detail/ 
and in 1900 he figured the pollen-tube ‘in pines/ when just 
above the archegonium, showing two sperm-cells of equal size. 
Blackman (’98) did not study the growth of the pollen-tube, 
but accepted Dixon’s work as authoritative. 
Professor Atkinson (’98) stated that the sperm-mother-cell 
in Pinus divides into two sperm -cells after having passed into 
the pollen-tube. 
