loa 



SCIENCE. 



[N. S. Vol. XVII. No. 420. 



the materials stored up in the spore, or 

 even lives parasitically upon the sporo- 

 phyte, as in Selaginella, thus reversing the 

 relation of sporophyte and gametophyte 

 found in the lower arehegoniates. 



All of these modifications are in the 

 direction of economy of water, in accord 

 with the needs of a more and more pro- 

 nounced terrestrial habit. 



Just as heter.ospory arose independently 

 in several groups of pteridophytes, so also 

 the seed habit— the final triumph of the 

 terrestrial sporophyte over the primitive 

 aquatic conditions— developed more than 

 once. The female gametophyte, included 

 within the embryo-sac, develops without 

 the presence of free water, and the ger- 

 minating pollen-spore also absorbs the 

 water it needs from the tissues of the pistil, 

 through which the tube grows very much 

 as a parasitic fungus would do. Except 

 in a very few cases, the male cells of the 

 seed plants have lost the cilia, the last trace 

 of their aquatic origin, and are conveyed 

 passively to the egg-cell by the growth of 

 the pollen-tube. 



Once firmly established as terrestrial 

 organisms, and the problem of water sup- 

 ply solved, the further development of the 

 seed plants is too familiar to need any spe- 

 cial comment here. The great importance 

 of water in affecting the structure of land 

 plants is seen in the innumerable water- 

 saving devices developed in the so-called 

 ■'xerophilous' plants, seen in its most ex- 

 treme phase in such desert plants as cacti, 

 or in the numerous epiphytes, like many 

 orchids and br.omeliads. 



In short, it is safe, I think, to assert 

 that of all the extrinsic factors which have 

 affected the structure of the plant body, 

 the relation to the water supply holds the 

 first place. The most momentous event 

 in the development of the vegetable king- 

 dom was the change from the primitive 

 aquatic habit to the life on land which 



characterizes the predominant plants of 

 the present. 



Douglas Houghton Campbell. 



SECTION A, MATHEMATICS AND 

 ASTRONOMY. 



Vice-President — Professor George Bruce Hal- 

 sted, Austin. 



Secretary — Professor Charles S. Howe, Cleve- 

 land. 



Member of Council — Professor John M. Van 

 Vleck. 



Sectional Committee — Professor G. W. Hough, 

 Vice-President, 1902; Professor E. S. Crawley, 

 Secretary, 1902; Professor G. B. Halsted, Vice- 

 President, 1903; Professor C. S. Howe, Secretary, 

 1903; Professor Ormond Stone, five years; Pro- 

 fessor J. R. Eastman, four years; Dr. John A. 

 Brashear, three years; Professor Wooster W. 

 Beman, two years; Professor Edwin B. Frost, one 

 year. 



General Committee — Mr. Otto H. Tittmann. 



Papers were read as follows: 



Deflections of the Vertical in Porto Rico: 

 Otto H. Tittmann, Superintendent U. 

 S. Coast and Geodetic Survey. 

 Mr. Tittmann gave an account of some 

 large deflections of the plumb line in Porto 

 Rico. Their existence was first noted by 

 Count Canete del Pinar, of the Spanish 

 Hydrographic Commission, which extended 

 a triangulation around the island, but the 

 war or other causes prevented a verifica- 

 tion by that commission. The Coast Sur- 

 vey, however, in the course of its surveys 

 extended a triangulation across the island 

 from San Juan to Ponce and proved their 

 existence beyond question. These deflec- 

 tions are so great that they affect the ear- 

 togx-aphic representation of the island, and 

 a mean latitude had to be adopted, with 

 the result that the northern coast line, as 

 now shown on the maps, had to be moved 

 by half a mile further south and the 

 southern coast line by the same amount 

 further north than would have been the 

 case if the astronomical latitude had been 

 used. 



