1869.] SENATE—No. 60. 15 
ceous matter, while softened by maceration, or rather exhibit 
the transition of the vegetable from its natural state to a plastic 
one before its hardening by heat and mineralization. The 
peculiar dimorphism of the fossil plants of Rhode Island has 
not been observed elsewhere, not even in the anthracite basin 
of Pennsylvania. 
The most important part of the work which, according to the 
directions of Professor Agassiz, should have been begun this 
year in the Museum, has been left nearly untouched, for reasons 
stated below. In the former report, (1867, page 15, § 12,) 
allusion has been made to the immense and most valuable col- 
lection of palms, fern-trees, and other species of equatorial 
plants, carefully selected as most appropriate materials for the 
comparative anatomy of the fossil floras of divers formations, 
and brought from Brazil to the Museum by its director. To 
fulfil the plan suggested, and to give to these specimens their 
real value, it is necessary to prepare them as models or samples 
for comparison, by making sections in various planes of direc- 
tion, in order to show their internal structure, and displaying 
some of the surfaces under a high polish, while in others thin, 
transparent lamellae should be cut and adjusted under glass for 
microscopical examination, &c., &c. Such a work demands 
the greatest care, not only in the selection and in the prepara- 
tion of the specimens, but also in their arrangement, in order 
that every part destined to anatomical comparison, either as a 
whole organ or as a part of it, can be easily found and referred 
to its proper species and place, without possibility of a mistake. 
In attempting to beein the purposed work of preparation, it 
became evident— 
1. That we had not yet in the Museum instruments which 
could be employed for that kind of work, without endangering 
the value of the specimens; and 
2. That it was impossible to obtain sufficient room to have 
all the specimens conveniently disposed for a preliminary exam- 
ination. For it is important, before beginning the anatomy of 
various species, to have under view all the specimens by which 
they are represented, in order to first exactly determine them, 
and afterward to select for preparations the parts or organs 
most appropriate to the end. As the Brazilian specimens are 
mostly of great size,—some of them whole trees, with leaves 
