200 BOTANICAL GAZETTE [September 



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to the dorsal surface, is less at the corners than in the other parts. The lowest 

 part of a pit therefore corresponds to the outermost 



point 



vertieft. 



Oberflache 



ungcfiihr den die Grube umgrenzenden Theil derselben von dem inneren Theile 

 abschneidet. Aus den so entstandencn Aussenzellen geht nun das ganze, mit Luft- 

 niumen durchzogene Gc^\-cbe hervor. Vorcrst wird durch das in gleichcr Kichtung 

 fortschreitende Wachsthura das Griibchen weiter vertieft und so zum Canale, and nun 

 erfolgt in jcder Ausscnzelle eine der fniheren parallele Theilung. Der Canal durch- 

 setzt nun zwci ZclUagcn, deren ausscre zur bleibenden Oberhaut wird, wiihrend aus 

 der inneren Zellscliicht die ganze unter der Oberhaut liegcnde Lufthohlenschichte 

 hervorgcht.— Untersuchungen iiber die Lebermoose 4:10. 1879. 



7 In Zusammenfassung der iiber die Bildung der Luftriiurae und SpaltofFnungen 

 ebcn gegcbenen Ausfuhrungcn ergibt sich also, dass die Luftkammern nicht im Gewebe 

 durch Auseinandenvcichen der Zellen entstehen, auch nicht durch eine von aussen 

 nach inncn fortschreitende Spaltung; sondem dass sie Einsenkungen der OberSache 

 dar5tellcn,.die dadurch gebildct warden, dass bestimmte Punkte der Oberflache durch 

 rascheres Wachsthum benachbartcr Partieen uberwachsen werden.— /. c, p. 12- 



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originally lying in the surface, which wall remains short, and the parts of the 

 wall bounding the pit are parts of the originally outer walls, or have arisen from 

 them. If this mode of growth be continued, the pit will of course be deepened. 

 Now there occurs in each cell a division parallel to the surface, which separates 

 approximately the part surrounding the pit from the inner part. From the exterior 

 cell thus formed, there arises the whole of the tissue pervaded by air chambers. 

 First of all, the pit becomes farther deepened into a canal by progressive growth 

 in the same direction, and now there follows, in each outer cell, a division parallel 

 to the earlier one. The canal now penetrates two layers of cells, of which the outer 



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becomes the permanent epidermis, while from the inner arises the entire tissue 

 containing the air chambers lying beneath the epidermis. 



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He continues:^ 



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By way of summary of the foregoing exposition of the formation of air 

 chambers and stomata, it may be said that the air chambers do not arise in the 

 tissue by the separation of cells, nor by a progressive splitting from outside inward; 

 but that they represent depressions of the surface, which are formed by definite 

 points of the surface becoming overgrov^-n by the more rapid growth of neighbor- j 



ing parts. 



This investigation Leitgeb extended by a study of the stomata of 

 Marchantiaceaej an account of which, published in 1880 (/. c,^ foot- 

 note 3), was reprinted, with only a few unimportant verbal changes, 

 in the last part of the Untersuchungen. After declaring the homology 



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of the air chambers and canals of Marchantiaceae with those of 



Wachsthumvorgang noch weiter eingehalten unrd, wird das Grubchen selbstverstaridlich 



