BRYOLOGICAL PAPERS 

 I. THE ORIGIN OF AIR CHAMBERS 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY, 100 



Charles R. Barnes and W. J. G. Land 



(with twenty-two figures) 



The air passages in certain tissues of the vascular plants are so 

 prominent as to attract instant attention when a section is examined. 

 Inasmuch as new cells are produced by division, and the partitioning 

 wall is a joint product of the two severed protoplasts, a-priori reason- 

 ing leads to the hypothesis that intercellular spaces arise by the 

 secondar}^ splitting of the membrane, on account of unequal growth 

 and turgor. This hypothesis is abundantly verified by obsen^ation, 

 and there remains no doubt whatever that the aerating passages of 

 vascular plants are formed in this manner. 



When intercellular spaces were observed in liverworts, it was 

 natural to assume that they took their origin in the same fashion. 

 In the Anthocerotales, intercellular spaces of the triangular and 

 quadrangular type, familiar in the pith parenchyma of vascular plants, 

 occur in both gametophyte and sporophyte. We are not aware that 



+ 



the origin of these has ever been supposed to be in any way different 

 from that of similar spaces elsewhere. The origin of the mucilage 

 clefts and chambers of Anthoceros and Dendroceros is definitely 

 ascribed by Leitgeb' to cleavage, and he has been quoted in all 



textbooks. 



In the Marchantiales, however, the canals and air chambers in 

 the upper portion of the thallus are so large and extraordinary in 

 architecture, that it was questionable whether they arose in the familiar 

 fashion, or had some peculiar origin. Hopmeister^ describes the 

 formation of the air chambers in the gametophore of Marchantia 

 polymorpha in these words: 



Close under the arched upper surface of the receptacle of Marchantia .... 

 numerous air cavities are formed, even before the first appearance of the arche- 



I Leitgeb, H., Untersuchungen iiber die Lebermoose 5:4; i3ff-> 3^- 1879. 



2 Higher Cr>*ptogamia 117. 1862, 



197] 



[Botanical Gazette, vol. 44 



