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 egg. 



The fecundation of the allied Cycas revoluta of Japan has been 

 studied by the Japanese botanist Ikeno ; ft that of Zamia jloridana and 

 Z. pumila of the southern United States by Dr. H. J. Webber, of the 

 United States Department of Agriculture. b Doctor Webber found 

 the mature spermatozoids of Zamia to be the largest known to occur 

 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 — cytoplasm with 

 cytoplasm and nucleus with nucleus. c 



With abundance of living material at hand, the stud} T of Cycas 

 circinalis along the lines followed by Ikeno and Webber could not fail 

 to yield interesting and important results. 



• DISPERSAL OF PLANTS BY OCEAN CURRENTS. 



On the sandy beaches which form a groat 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 the} r 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 rnudd}' 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 uber die Entwickelung, etc. Jahrbiicher fur wissensch. 

 Botanik, 32, 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. 



cldem., p. 85. 



