CHARACTERISTICS OF THE FLORA. 25 
and among the material that is suggestive rather than instructive—trag- 
ments and indications of other species not sufticiently well represented to 
be described in full—there are perhaps 30 other species, including seeds 
and fruits, of which the connection with the plants that bore them is con- 
jectural. Most of the species enumerated in this list are represented by a 
large number of individuals, and the degree of preservation of the speci- 
mens is such that it is very satisfactory material for study as far as it goes; 
but it is evident that only a beginning has been made in gathering the 
fossil plants of the Amboy Clays, and probably for years to come consider- 
able additions will be made annually to that flora, so that the present 
memoir can be properly regarded as only the commencement of a great 
work. The partial view of the subject here given will be recognized by 
all those who are interested in it, and not too much weight will be given to 
such portions of the memoir as consist in descriptions of unique specimens 
or fragmentary material. 
Some special difficulties have stood in the way of making collections 
of the plants of the Amboy Clays. These clays have come to be a most 
important element in the resources of the State, and they are the basis 
of a great industry. The clay beds have been opened at a great number of 
points, and as the different layers are the products of changing physical 
conditions, and probably mark the lapse of considerable intervals of time, 
it is not strange that many differences should be noticeable in the fossil 
plants of the various beds. 
The greater number of the fossil plants now described are from the 
middle bed in the series—the Woodbridge clay bed—while we have not a 
few of the plants characteristic of the lower or Raritan beds, opened at 
Sayreville, and of the upper or South Amboy beds. Not enough material 
has been obtained from the South Amboy and Sayreville beds, however, to 
enable us to form a clear idea of the phases of vegetation prevalent at the 
time when these different deposits were made. We have learned that there 
is certainly considerable difference in the grouping of the plants in the 
three beds, and it is also probable that there are species which are not only 
characteristic of but confined to each of the three great divisions of the 
clay series. 
