36 BOTANICAL GAZETTE [JULY 
In Naias and Zannichellia Campbell® found an axial row of — 
two or three cells the lower of which alone became the embryo- 
sac. The development was normal up to the point where the 
polar nuclei were formed. The free egg-nucleus and synergids — 
and the minute antipodal cells were very characteristic; but no / 
fusion of polar nuclei was observed, and he doubts if it ever ‘ 
occurs. The enlarged basal nucleus is always present from this — 
stage onward, but is not separated by a wall from the main cavity se 
as in Potamogeton and Sagittaria. Campbell believes with Schaff- _ 
ner that this is a product of the first division of the definitive : 
nucleus, but also admits that it may be the lower polar nucleus — 
alone, while the upper has gone to form the endosperm. 
FERTILIZATION, 
The stages representing the various steps in the process of — 
fertilization are rarely met with in this plant. Several good | 
preparations were obtained, however, and these will form the — 
basis of the following description. 2 
The pollen tube enters the embryo-sac through the micro- 
pyle at a point directly behind the egg. In its course it passes” 
close to the partially disintegrated synergid, but the tube t 
quite slender and scarcely inflated after entering the embryo-sa¢, 
thus differing decidedly from Sagittaria, in which Schaffner 
described the inflation as very marked. : 
The two sperm nuclei were last noted in the mature pollen 
grain where they were both inclosed in the same cell-wall. The: 
remain united even during their trip down the pollen tube to the” 
embryo-sac and enter the egg together. Fusion of the egg a! 
sperm nucleus was not observed. The stage immediately pt 
ceding this was found however, and is figured in fig. 22. . Her 
the egg is easily recognized, and lying in close proximity to it, 
indeed even touching it, are the sperm nuclei. In reality only 
one actually touches the egg nucleus. The other lies at the sid 
or even at the back of the first, and is already in the process ° 
5 CAMPBELL: A 
: morphological study of Naias and Zannichellia. Proc. Calih 
Acad. Sci. I. 1:1, 1897. 
