1904] CHRYSLER—CENTRAL CYLINDER 179 
show fern-like characters is a fact of considerable phylogenetic sig- 
nificance. The evidence concerning the extrastelar or intrastelar 
origin of the pith is not so plain, but from the method of closure of 
the cotyledonary gap in Peltandra and Symplocarpus and of the foliar 
gaps of Trillium, I am led to believe that the tissue in question has 
been included; the hypocotyledonary region in Peltandra and Sym- 
plocarpus also suggests the unity of extrastelar and intrastelar tissues. 
Narrowness of the gaps would account for the failure of the endoder- 
mis and cortical tissue to enter through the foliar gaps in Acorus, 
and the absence of internal endodermis in such plants as Maianthe- 
mum may be ascribed to degeneration of such a layer as is found in 
the lower part of the stele in Symplocarpus but disappears in the 
higher regions of its stele. Thus it appears that the terms “cortex” 
and “pith” should be used only in a topographical sense, and not as 
implying a difference of origin, for morphologically they must be 
regarded as identical, as regions of the “(fundamental tissue,” using 
this term in the sense of Sacus and DeBary. Hence if the term 
“stele” is used, it should be restricted to the vascular elements of the 
central cylinder, as is insisted on by FARMER and Hirt (2). Further, 
the researches of ScHouTE (14) have shown that HANsTEIN’s derma- 
togen, periblem, and plerome do not correspond to VANTIEGHEM’S 
epidermis, cortex, and stele, so that there no longer appears to be 
any necessity for postulating a common origin for all the tissues found 
Inside the endodermal ring. On the whole, then, the development of 
the stele in the two families in question appears to support the gener- 
alizations made by JEFFREY. 
MEDULLARY BUNDLES.—The writer is inclined to believe that 
these did not originate as leaf traces, but as strands to which leaf 
traces subsequently became attached. This tentative view rests upon 
the following considerations: 
1. The tendency of the monocotyledonous stele to break up into 
Segments makes it easy for a strand to leave its vertical course at the 
Periphery of the stele and run for a distance in the medulla; such a 
strand may at a higher level return to its original course, or may join 
the stelar ting at the opposite side. Both of these conditions are to 
seen in the young stele of Smilacina stellata. In Maianthemum 
the first medullary strands to appear do not come in contact with the 
