1908] BARNES &• LAND—CUPULE OF MARCHANTIA 409 



elevation continues the line of the posterior rim and so suggests the 

 circular cup of Marchantia. 



The superficial origin of the gemmae is thus perfectly clear. 

 They cannot be considered as in any sense homologous with the 

 chlorophyllose filaments of an opened air chamber, nor has the cup 

 any relation to the epidermal roof. The thicker part of it contains 

 air chambers, and the thin part is simply a scalelike outgrowth of the 

 epidermis. The difference between an air-chamber and a cupule 

 becomes especially striking when a cupule originates near an air 

 chamber, as shown in figs. 2, 7, 10, 14, at /. Then, although the 

 gemmiparous cells are seen to be superficial, they evidently represent 

 cells that otherwise might produce not only the roof, filaments, and 

 floor of an air chamber, but also a considerable portion of the thallus 

 beneath the air chamber. In figs. 2, 7, 10, the line, /, t, can be 

 followed clearly, showing how deeply the gemmiparous cells involve 

 the tissues of the thallus. It is not surprising, therefore, that the 

 gemma cup, though of superficial origin, is a depression in the thallus, 

 and that air chambers clothe its sides. 



Incidentally we may add that the origin of the gemmiparous cells, 

 as herein shown, precludes our acceptance of Goebel's conception 

 that in Marchantia the gemmae are homologous with "slime papil- 

 lae." 5 The formation of mucus cannot be considered as a special 

 function of any particular cells, though the so-called slime papillae 

 have the name of "secreting" it. In fact young cells of very different 

 origin and fate form mucus, and it is doubtful if any of the younger 

 ones fail to form it. These "papillae" are purely superficial organs, 

 and scarcely agree with the gemmiparous cells in anything except 

 that at one time both project above the surface. How can the latter, 

 which involve so considerable a part of the thallus, corresponding, 

 as above shown, to the whole air chamber region and two or more 

 layers of cells below it, be properly likened to such transient and 

 superficial outgrowths as the "slime papillae"? To pronounce the 

 two homologous throws no real light upon the nature of the gemmae, 

 for the production of which there is such early and striking preparation. 



The University of Chicago 



s Goebel, K., "Die Brutknospe von Marchantia und Lunularia kann auch als 

 einer Schleimpapille homolog betrachten werden." Archegoniatenstudien XII. 

 Flora 98:314. 1908. 



