72 USEFUL PLANTS OF GUAM. 
and in the pollen tube are produced spermatozoids provided with 
minute movable cilia by which they are propelled. These are dis- 
charged over the archegonia and fecundate the eee. 
The fecundation of the allied Cycas revoluta of Japan has been 
studied by the Japanese botanist Ikeno:@ that of Zui floridana and 
Z. pumila of the southern United States by Dr. H. JJ. Webber, of the 
United States Department of Agriculture.’ Doctor Webber found 
the mature spermatozoids of Zamia to be the largest known to oceur 
in any plant or animal. They are even visible to the naked eye. 
He kept them alive in sugar solutions and found their motion to be 
due mainly to the action of cilia. 
In fecundation the entire spermatozoid enters the egg cell, swimming in between 
the ruptured neck cells. Sometimes two or three spermatozoids enter the same egg, 
but only one is used in fecundation, the others perishing. On entering the upper 
part of the egg cytoplasm the nucleus escapes from the spermatozoid, being left 
slightly in rear of the active ciliferous band. The plasma membrane of the sper- 
matozoid entirely disappears, seeming to unite with the cytoplasm of the egg, and 
this allows the spermatozoid cytoplasm also to unite with the egg cytoplasm and 
leaves the nucleus free. The nucleus passes on to the egg nucleus, with which it 
unites. Fecundation thus consists of a fusion of two entire cells—eytoplasm with 
cytoplasm and nucleus with nucleus, ¢ 
With abundance of living material at hand, the study of Cycas 
circinalis along the lines followed by [keno and Webber could not fail 
to yield interesting and important results. 
DISPERSAL OF PLANTS BY OCEAN CURRENTS. 
On the sandy beaches which form a great part of the east coast of 
Guam there is always a line of drift, just above high-water mark, 
which is rich in seeds, fruits of various kinds, and driftwood brought 
by the great ocean current which sweeps across the Pacific from east 
to west. Sometimes the seeds and logs are riddled with teredo bor- 
ings or are covered with barnacles, but often they appear fresh and 
little worn by the erosion of the waves and sand. Many of the seeds 
are dead; some of them are alive and capable of germination. Not all 
the species which reach the island have gained foothold there. The 
fruits of plants growing in muddy estuaries or mangrove swamps, for 
instance, can not establish themselves on a clean sandy beach. 
Germinating fruits of Rhizophora and Bruguiera are frequently cast 
up only to die, and nuts of the nipa palm, though found in perfect 
condition, can establish themselves only near the mouths of streams 
where the water is brackish. Though coconuts are of frequent 
“S, Ikeno, Untersuchungen iiber die Entwickelung, ete. Jahrbiicher fiir wissensch. 
Botanik, 82, Heft 4, p. 557, 1898. See list of works. 
’ Webber, Herbert J., Spermatogenesis and fecundation of Zamia. U.S. Dept. 
Agriculture, Bureau of Plant Industry, Bull. No. 2, 1901. See list of works. 
¢Idem., p, 85. 
