SEXUALITY IN PLANTS—JOHNSON. 389 
push into the receptive tip of the living egg and saw the character- 
istic odspore wall formed in consequence. This, except for the less 
satisfactory observations made on Vaucheria a year previous by the 
same worker, is the first case recorded of the observation of the 
actual union of male and female cells in any plant. Such a union 
of the protoplasmic masses of the two sexual cells was soon shown to 
be a characteristic feature of fertilization in a number of alge. Thus 
De Bary saw it in Spirogyra (1858), and Pringsheim (1869) repeatedly 
observed the gradual fusion of the motile gametes of Pandorina. It 
was nearly 30 years later, however, that this phase of fertilization was 
first seen in seed plants by Goroschankin and Strasburger. 
The workers on this problem were on the lookout for further details 
of the process of fusion, and even knew rather definitely what they 
were looking for, but failed to discover it from lack of proper methods 
of preparation of material. Thus, Strasburger, in 1877, carefully 
studied the process of conjugation in Spirogyra and found that 
“Hautschicht fuses with Hautschicht, Kernplasma with Kern- 
plasma’’—‘“‘The chlorophyll bands unite by their ends ’’—and he then 
goes on to say of the feature that evidently interested him most, “the 
cell nuclei of both cells, however, became dissolved; the copulation 
product is without a nucleus.”’ Two years later Schmitz (1879), 
when studying hematoxylin-stained material of this alga, was more 
fortunate. He saw the two nuclei in the zygote, as he says, “ap- 
proach nearer and nearer, come into contact and finally fuse to a 
single nucleus.” This observation by Schmitz is an important one, 
for in it we have the first clear statement that the nucleus of the male 
cell passes over intact to the female cell, there to fuse with the female 
nucleus. 
Strasburger had, it is true, seen a second nucleus fusing with that 
of the egg in the archegonia of Picea and Pinus in 1877. He did not, 
however, really know the source of this second nucleus, though he 
suspected some relation to those that are present earlier in the tip 
of the pollen tube. These tube nuclei he says are dissolved just 
before fertilization, and then just after fertilization, to quote (1877): 
The male nucleus formed from the contents of the pollen tube is found now near the 
end of the tube, now near, or in contact with, the egg nucleus. * * * The proto- 
plasmic contents of the pollen tube, I hold, passes through the (imperforate) tube- 
membrane in a diosmotic manner. 
The fertilization of the gymnosperms, because of their large eggs, 
pollen tubes, and nuclei, was at this time being studied by a number 
of workers. One of these, Goroschankin, in 1883, was able to demon- 
strate that in Pinus pumilio the pollen tube opens at the end, and 
that through this pore the two male cells pass bodily into the egg. 
Goroschankin’s mistake, in supposing both male nuclei to fuse with 
the egg nucleus, was corrected by Strasburger the following year. The 
