[kirsco] CERTAIN STRUCTURES IN THE PTERIDOPHYTES 361 
papillæ (Papillen) become separated from the mother cells by means 
of walls; in older stipes they are lignified and provided with reticulated 
thickenings. They are structures related to the thyloses of the Mono-, 
and Dicotyledons.” 
It is thus seen that Thome is so far right in that he sees the rela- 
tion between the protoxylem, the canal, and the cells in the canal. As 
regards the development, however, he is wrong both in the case of the 
canal, and in that of the thyloses. In the many preparations examined 
by the writer no papillar projections into the canal from the bordering 
cells have been observed, the cells filling the canal being bladder-like 
outgrowths from the free ends of the wood-parenchyma cells. These 
outgrowths are almost immediately cut off from the mother cell by a 
wall, so that even in comparatively early stages of thylose formation, 
the thyloses have distinct walls of their own. 
Continuing, Thome says (22, 125): “Dippel describes them in 
Osmunda, and Russow also meant these in his description of the struc- 
tures which he calls “ Liickenparenchym,” although, in his “ Betrach- 
tungen uber Leitbundel und Grundgewebe” (Dorpat, 1875, p. 41), he 
cites Dippel’s description without connecting the phenomenon with his 
“ Liickenparenchym.” 
Thome here does not seem to see that Russow and Dippel did not 
interpret the structure at all correctly, and merely states that they ap- 
plied different names to the phenomenon. As has been noted above, 
Russow observed no connection whatsoever between the break in the 
protoxylem and his “ Liickenparenchym,” interpreting the latter as a 
form of lacunar parenchyma peculiar to the vascular bundle. 
Dippel also, as far as can be made out from his own statement, did 
not see this connection, and what is more, owing to this very fact, con- 
fused the tannin and mucilage-bearing cells with the thyloses, thus being 
led to give an erroneous interpretation of the function of these thylosal 
strands. Thome does not say anything about the function or purpose 
of either the canals or the thyloses in the fern stipes described by him, 
nor does he criticise Dippel’s views as regards the function of the thy- 
loses. Thus he either did not understand the purpose of these structures, 
or left this point out of consideration. 
“Potonié and Terletzki also mention these structures; the latter 
investigator calls them “ Stumpfzellstringe.”—They occur in all mature 
(alteren) stipes of ferns in the position of the protoxylem groups, most 
exquisitely in the Cyatheaceæ.” 
Here again Thome fails to note that Terletzki only saw one stage 
of the structures in question, and that outside of the proximity of the 
