FEBRUARY 1, 1901.] 
relationship to the modern Siphoneae, but 
an extended study of American forms leads 
to hesitation in giving this opinion un- 
qualified acceptance. Several years since, 
the belief was expressed that there were 
grounds for supposing a relationship with 
Laminarieae, and the genus Lessonia was 
cited as likely to afford the best means of 
comparison, but the impossibility of secur- 
ing suitable material caused such studies to 
be deferred. Recent studies by MacMillan 
have given us a detailed account of the 
‘morphology of this extremely interesting 
but not readily accessible plant, and from 
material which he has kindly supplied the 
writer, it is to be noted that very striking 
points of resemblance to Nematophycus ap- 
pear. Without entering into details on the 
present occasion, it may suffice to indicate 
that similar growth layers, the presence of 
a distinct cortical structure, the general 
disposition of the elements as seen in trans- 
verse section, and the presence of radial 
spaces, occupied by elements of the medulla 
which there assume a horizontal position 
-and develop special relations to one an- 
-other, are all features which point with 
considerable force to possible relationship. 
-Beyond these facts, however, our present 
‘knowledge respecting the phylogeny of this 
group of plants will not permit us to go. 
The Bryophytes constitute another group 
which, from their delicate organization, are 
not likely to be found either in very con- 
siderable numbers or in a very perfect state 
of preservation as fossils. They neverthe- 
less occupy a most important position in 
plant evolution, since they are considered 
to constitute the connecting link between 
the green alge and the higher vascular 
plants, their derivation from the former be- 
ing through the thalloid liverworts, while 
their algoid ancestry also appears in the 
filamentous protonema of the true mosses 
and in the motile spermatozoids of the en- 
tire group. From the phylogenetic position 
SCIENCE. 
173 
of these plants as determined by a study of 
existing forms, we are led to infer that they 
must have had their origin in very early geo- 
logical times—antedating the more fully or- 
ganized terrestrial forms of which they are 
to be considered the ancestors. There is 
thus good reason for supposing them to 
have flourished as early as Devonian or 
even Silurian time, but the evidence deriv- 
able from the rocks shows no recognizable 
remains of these plants until we reach the 
later Mesozoic, while it is not until Tertiary 
time that they become clearly defined. It 
is, therefore, reasonably certain that the so- 
lution of questions relating to the origin of 
this group must rest altogether upon evi- 
dence derived from a study of existing 
species—to such, fossil botany has as yet 
contributed nothing. 
From their more durable structure, which 
offers a higher degree of resistance to the 
operation of decay, the vascular plants have 
always been found in the best state (some- 
times remarkably perfect) of preservation, 
and they have therefore always presented 
the best of opportunities for phylogenetic 
studies, more especially in consequence of 
the great abundance of their remains and 
the increased probability of deriving data 
of permanent value from them. In con- 
sidering the distribution of these plants in 
geological time, one is impressed not so 
much with their often extensive vertical 
range, aS with the abruptness with which 
special types appear through representa- 
tives of a high degree of organization. This 
has already been noted in the case of the 
Thallophytes, and among the vascular plants 
itis no less remarkable. The ferns which 
first appear in the Devonian are represented 
not only by foliage and fruit, but also by 
stems of large dimensions ; the Cycads ab- 
ruptly appear in the Jurassic and Cretace- 
ous while the Angiosperms as suddenly ap- 
pear in the Mesozoic, where they gain great 
prominence in the Cretaceous formation. 
