106 PROGRESS OF MICROSCOPICAL SCIENCE. [“onmai ace Tae. 
ture. The wood, he says, is converted into chalcedony. The tissues 
are, on the whole, not well preserved, although occasionally specimens 
occur in which every cell and vessel is clearly defined. Unger de- 
tected in some specimens the branching mycelium of a parasitic 
fungus, penetrating the cavities of the large ducts, to which he gave 
the name of Nyctomyces entoxylinus.* In none of the large series of 
microscopic preparations which Mr. Carruthers examined (21 from 
the specimens collected by Prof. Owen, two from the Bryson Collec- 
tion, and two from that of Robert Brown) was he able to detect this 
fungus. In all of them the ducts are filled with transparent chal- 
cedony, which occasionally shows a dark, amorphous and irregular, 
sometimes branching core, passing down the centre. The chalcedony 
is more or less filled with minute bodies resembling transverse hex- 
agonal prisms of quartz; but they are thin plates or cavities pene- 
trating the chalcedony in every direction. They have an amorphous 
centre, and exhibit concentric lines of growth. They do not affect 
the light differently from the substance in which they are imbedded, 
when examined by the polariscope. Newbold refers to a specimen 
shown him by M. Linant, at Cairo, which had apparently a somewhat 
similar structure, but Mr. Carruthers thinks it must have been on a much 
larger scale, as he does not speak of using any magnifying power in 
examining it. He says it “had the hollow lined with a white chal- 
cedony-like silicious substance, full of small cells resembling those of 
a honeycomb.” t The stems, as determined by Robert Brown, and 
confirmed by Unger, belong to Angiospermatous dicotyledons, and are 
made up of the tissues that enter into the composition of such plants. 
The wood consists of slender prosenchyma, abundantly penetrated by 
large ducts, which occur singly or arranged, two, three, or even more 
together. The walls of the ducts are marked with small, regularly- 
arranged oval, or somewhat compressed hexagonal, reticulations. 
Transverse diaphragms break up the ducts in well-preserved specimens 
into oblong compartments about twice as long as broad. The medul- 
lary rays are abundant, and form a considerable proportion of the stem. 
The concentric layers of wood are not so well defined as one generally 
finds them in dicotyledonous stems, because of the irregular manner in 
which the ducts occur throughout the year’s growth. In this respect 
they resemble the walnut rather than the oak? Mr. Carruthers remarks 
that the structure of stems have not been hitherto sufficiently regarded 
by systematic botanists, and recommends that attention be more 
directed to this subject. In conclusion he says that “owing to this 
he cannot go beyond R. Brown in saying that these stems are di- 
cotyledonous, they are not coniferous.” 
The Metamorphoses of the Gnat.—Myr. Marshall communicates to the 
‘Proceedings of the Birmingham Natural History Society’ a nice 
paper on this subject. He gives two plates showing the successive 
transformations of the larva. The powers employed are very low, as 
the object of the transformations within the ovum have not been 
studied. 
* «Chloris Protogea,’ p. 8, Tab. L., Fig. 7. 
+ ‘Quart. Journ. of Geol. Soce., vol, iv., p. 353. 
