1907] 



BARNES ^ LAND— ORIGIN OF AIR CHAMBERS 



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209 



the tissues concerned with the formation of air chambers have an 

 oedematoiis look; being soon greatly swollen, with scanty contents. 



Fig. 13. — Conocephahis conicus: a, apical cell; 7-7, air chambers. 



In consequence of the excessive turgor, apparently, the splitting is 

 very prompt and complete, so that the young internal space is difficult 

 to find. The air chambers de- 

 velop rapidly, and ''blow up," 

 so to speak, within a short dis- 

 tance of the apex, only the ragged 

 walls and roofs, in section like a 

 letter Y, remaining for a time. 



Fig. 14. — Dumortkra hispida (?): 

 a, apical region; /, 2, air chambers. 



Fig. 15. — Dumortiera hispida. Older 

 air chambers, deformed by excessive 

 turgor. 



It will be observed that the air-chamber region in Marchantia, 

 Lunularia, Conocephalus, and Dumortiera is superficial. By no 



