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SCIENCE 



[N. S. Vol. XXV. No. 634 



held at Columbia University on December 

 27 and 31, and at the museum of the New 

 York Botanical Garden on the morning of 

 December 29. At the latter meeting the 

 presidential address — 'The Organization of 

 Certain Ccenobic Plants'— was delivered 

 by Past President R. A. Harper. After 

 the meeting a luncheon was served 

 in the laboratories of the garden to the 

 members of the society and Section G of 

 the American Association for the Advance- 

 ment of Science. 



Abstracts of the technical papers read 

 follow : 



Figures Produced by Protoplasmic Stream- 

 ing in Fungi and Slime Moulds: Pro- 

 fessor E. A. Haeper, University of Wis- 

 consin. 



The Origin of Air-Chamibers in Liver- 

 worts: Professor C. R. Barnes and Dr. 

 "W. J. G. Land, University of Chicago. 

 Intercellular spaces are formed in higher 

 plants by the splitting of cell walls and 

 the separation of the cells by their unequal 

 growth and turgor. The air-chambers of 

 liverworts, especially of Marchiantiales, are 

 so peculiar in form that some peculiar 

 mode of origin was looked for. Hof- 

 meister ascribed their formation in Mar- 

 chantia (1862) to the detachment of the 

 epidermis and its lifting by the plates of 

 cells which form the side walls. This view 

 made the air-chamber only a special form 

 of intercellular space. But Leitgeb con- 

 troverted this interpretation (1880), and 

 his view has been universally accepted for 

 a quarter of a century. He ascribes the 

 origin to a slower growth of the cells at the 

 point where four to six lateral walls meet, 

 and the consequent formation of a pit, 

 which becomes overgrown by adjacent cells 

 as it deepens. He emphasizes the state- 

 ment that the lowest point of the pit is the 

 original surface, and homologizes the air 

 chambers strictly with the pits, nearly 



closed at mouth, in which many sex organs 

 are sunk. 



The authors show that Hofmeister prob- 

 ably did not see the real origin of the air- 

 chambers, but only later stages in their 

 development; that Leitgeb 's observations, 

 correct as far as his descriptions and 

 figures show, were misinterpreted by him, 

 and do not account for the course of de- 

 velopment described; and further, his few 

 observations of the real origin were actually 

 distorted (according to his own confession) 

 to fit his theory of the homology of the air 

 chambers with sex-organ pit. 



Evidence can now be adduced, by means 

 of the superior technique available, which 

 shows beyond doubt that the air chamber 

 appears first as an internal intercellular 

 space, usually within two segments from 

 the apical cell. This space increases in 

 size, breaks out to the surface (rarely be- 

 ing met by inward splitting from the sur- 

 face), and sometimes deepens by further 

 splitting inward from the original point 

 of origin. The remainder of the develop- 

 ment is due to growth in all dimensions, 

 but chiefly parallel to the surface. Thus 

 the floor of the air-chamber, instead of 

 arising from the original surface and being 

 roofed over by adjacent cells, as is uni- 

 versally taught, is an internal surface, 

 formed, as in other plants, by splitting due 

 to unequal turgor and growth. Instead of 

 being homologous with the sex-organ pits 

 the air-chambers are strictly homologous 

 with intercellular spaces generally. 



Fertilization and Embryogeny in Ephedra 

 Trifurca: Dr. W. J. G. Land, University 

 of Chicago. 



In Ephedra trifurca Torr. the pollen 

 chamber extends to the female gameto- 

 phyte, and the necks of the archegonia are 

 freely exposed. The pollen grains rest in 

 the bottom of the pollen chamber in con- 

 tact with the female gametophyte. 



