i 9 i6] STARR— AYTONIA 49 



Vegetative body 



The thallus (fig. i) is dorsiventral, dichotomously lobed and 

 branched, with no groove on the dorsal side, but on the ventral 

 side (fig. 2) a thickened median region, covered thickly with scales 

 and rhizoids. The upper surface is green, showing purple at the 

 edges; the ventral is light along the central region, with broad 

 purple wings; the scales are in two rows, extending laterally from 

 the median line, arranged alternately; they are attached along the 

 posterior edge, lapping over those in front, and are shaped like the 

 half of a crescent and have one or two appendages, the scales being 

 purple and the appendages hyaline (fig. 3). Two appendages 

 seem not to have been reported before. 



The first rhizoids appear behind the first three or four pairs 

 of scales and then occur in great abundance between Che scales. 

 They are of two kinds, pegged and smooth, the pegged appearing 

 in bunches. They are deformed at the ends (fig. 4), but are not 

 branched. The smooth rhizoids vary greatly in size, and frequently 

 within the larger, smaller ones are produced (fig. 5) ; whether this 

 occurs only when the larger are injured could not be determined, 

 as most of the rhizoids were broken in collecting. The exterior 

 rhizoids, having heavy walls, appear much older than those inside. 

 This phenomenon is not uncommon in liverworts, often appearing 

 in Marchantia, in which pegged rhizoids sometimes occur within 

 plain ones. Dixon (9) also reports rhizoids within rhizoids in 

 Lnnularia cruciata, Dumortiera hirsuta, Conocephalus conicus, 

 Anthoceros punctatus, and Marchantia polymorpha. Weinert (17), 

 in a study of Marchantia and Conocephalus, says "lost rhizoids 

 are not regenerated, but other epidermal cells grow out into new 

 rhizoids," which is plainly the case here. A new cell or several 

 new cells just above the layer of old rhizoids push down into the 

 cavity of the old rhizoid. 



Structure 



The thallus shows the usual differentiation into thin wings of 

 spongy tissue and a thick median region composed of close colorless 

 tissue below and spongy chlorophyllose tissue above, the latter 



