KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 51. N:o 10. 5 
number more than two and that the stomata were probably situated in cavities 
under the epidermis exactly as in Nerium Oleander. "The round openings should 
be the entrances to these cavities. He also draws attention to the striking resem- 
blance between the rounded openings with their four to six bordering cells and the 
basal cells of many vegetable hairs, and considers, on the other hand, that we may 
have to do with the same case here. 
As far as KNOWLTON is concerned HoLM's criticism is sufficient. The cell- 
-walls he discerned and regarded as belonging to the guardian cells no doubt belong 
to the uppermost of the cell-layers which often lie between these and the epidermis, 
for, as we now know, stomata with more than two guard-cells do not occur in 
vascular plants. 
Though there is a great resemblance to the basal cells of vegetable hairs, it 
is not a case of such cells here, at least not in Ptilozamites. HoLM's comparison 
between the holes now in question and the entrances to ”eryptes stomatiféres” is 
somewhat far-fetched. The explanation is surely more simple, and there can be no 
doubt that the stomata were analogous with those of the Gymnosperms. 
Piilozamites was instituted in 1878 by NATHORST (1878 a, p. 21) for fronds 
having an intermediate position between Anomozamites SCHIMP., Plilophyllum MORR., 
and Otozamites BRAUN. According to his opinion at that time Ptilozamites differed 
from the first-mentioned genus in having radiating veins, and from the other two 
by the pinnae being attached by the whole of the base. Later on, however, he 
(1879, p. 59) states that the supposed difference from Anomozamites did not hold 
good, as broad pinnae have a venation which agrees perfectly with that of this latter 
genus. But now, instead, he regards the rounding of the proximal margin of the 
segments, their regular shape, and the greater thickness of the cuticle as good distin- 
guishing characters. 
As a very nearly related species, and as one probably belonging to Ptilozamites, 
NATHORST (1878, p. 51 and 1878 a, p. 23) also regarded Ctenopteris cycadea (BRNGN-). 
Since this proved to have a bipinnate segmentation (NATHORST 1880, p. 45) he (1880, 
p- 66) considered this feature to be characteristic of Ptilozamites, too. But as this 
supposition was not verified by any find whatever, he (1886, p. 122) proposed the 
use of the name of Ptilozamites for pinnate, and that of Ctenozamites, a new generic 
name, for bipinnate fronds that agree in other respects. Ctenozamites should be 
used instead of Ctenopteris SAP., since this name was already (1828) preoccupied by 
BLUME for a section of Polypodium (SMITH 1875, p. 184; NATHORST 1880, p. 66). 
Now, however, Ctenopteris is not used for any genus of living plants, and Prof. 
NATHORST thinks we had better readopt it for the fossil genus as a nomen con- 
servandum. 
As the agreement with Otozamites and Ptilophyllum is only superficial, both 
of them having, for example, their pinnae attached to the upper side of the rachis, 
it is above all Ctenopteris and Anomozamites that are very neariy related to Ptilo- 
zamites. 
