REPORT OF RESIDENT ENGINEER, DREDGING DIVISION. 189 were deposited in and around Gamboa while the lake was about elevation +70, and were distributed from there on the rising water into the various shoals in this neighborhood. This belief is strengthened by the discovery of an old bed of plants in the Chilibre River near its junction with the Chagres. The statement has been made that the plant here is not so prolific as the Florida and Louisiana variety, but the statement above made in regard to its seed development would seem to indicate that it is as able as the States plant in increasing and that the reason it has not spread all over the lake is that the current in the lake does not allow its distribution as a river does, and it is thought that this is the only reason that has allowed us to cope with it with a prospect of success. Instances are known where an old bed has been destroyed and no new plants sprouted from the seed until six months or more had elapsed, when a good growth started, new plants constantly coming up from seed, to the present time. Again old beds destroyed in shallow water in a very short time produced new plants from the seed, and in time these were pulled or destroyed, repeating the performance until the same area had been done over six or more times, and there is still a vigorous growth of young plants coming up. The vigor and habits of the plant are such that it is thought it could not be exterminated over a sluggish moving stream unless with very great expense, dividing the stream into districts, beginning the campaign from the headwaters and working downstream. As each district was cleaned up it should be constantly patrolled, not to allow a single plant to go to seed, the side marshes and tributary streams treated the same way, and it is thought this campaign would require at least two or three years' time, as from our own experience it is known that some seeds deposited in deep water require a year or more to germinate. The current is undoubtedly responsible for its distribution into other areas than that occupied by the parent plant, and when the plant can produce from 150,000 to 200,000 seed per year, be torn loose on a freshet, and travel the entire length of the stream to the sea, maturing and dropping its seeds the entire distance, it is no great wonder that it has not been conquered anywhere, so far as known. On our part, it is thought that our campaign against it began in time and assisted as it has been by the lack of a distributing current will be entirely successful, although the total extermination of this plant, owing to the delay in germination of some of the seeds, will require a careful inspection for possibly a year or more longer. SURVEYS. The usual surveys were made of the dredged areas in the canal prism, Cristobal Harbor, Toro Point, Margarita, Coco Solo, Limon Bay, and Balboa Inner Harbor; cross sections plotted, reports and estimates prepared. The general progress surveys were made every four months. Daily progress surveys were made of the channel at Cucaracha and Culebra slides; channel dragged and buoyed before passage of shipping. Topographic surveys were made of the Cucaracha and Culebra slides and the Obispo diversion. Routine clerical work, preparation of progress records, estimates, requisitions, etc., was satisfactorily performed during the year. Respectfully submitted. W. G. COMBER, Maj. Gen. GEO. W. GOETHALS, United States Army, Governor, The Panama Canal, Balboa Heights, Canal Zone. |