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BOTANICAL GAZETTE 



[OCTOBER 



rounded by a zone several layers deep of relatively small brown cells, which 

 has been developed by radial and longitudinal division during the increase 

 in size of the cells of the included tissue. At a distance of 2''"' from the 

 apex, the large cells, which have been filled chiefly with water, the walls hav- 

 ing merely a film of protoplasm, break down, giving rise to the ant galleries, 

 which are thus of lysigenous origin. The arrangement of the galleries is in 

 both cases regular, although not exactly the same, a main ventral longitu- 

 dinal gallery giving off two lateral series of galleries to the branches and 

 two vertical series leading to the leaf-cushions, branching soon after leaving 

 the ventral gallery to form two longitudinal series of dorsal chambers. Com- 

 munication with the external air is secured by short passages excavated in 

 the soft tissue of the younger parts of the stem by the ants themselves. 

 While the function of the galleries is still somewhat obscure, the large-celled 

 tissue seems to have been developed as a special water-reservoir, but its 

 early disintegration may indicate an important function in the galleries, as 

 aeration or to a slight extent absorption of water. There is no evidence that 

 the galleries are an adaptation on behalf of the ants. In P, carnosum the 

 marginal lobes upon which the sori are borne are reflexed at maturity so 

 that they are turned upward, this being possibly an adaptation to secure the 

 distribution of the spores during a strong wind, which would be most favor- 

 able for a high growing epiphyte. — J. Arthur Harris. 



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