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POPULAR SCIENCE REVIEW. 
A Monograph on Bog Mosses is being presented to the Royal Microscopical 
Society by Dr. Braithwaite, F.L.S., and is being published in the “ Monthly 
Microscopical Journal.” The number of that journal for February contains 
the first description of the genera and species, beginning with the genus 
Sphagnum. In the preliminary remarks the author gives the following 
account of the division of the group. Thus, he says, that in the arrange- 
ment of the species Bridel adopts two sections, Obtusifolia and Acutifolia ; 
and this plan is followed by Wilson in the “ Bryologia Britannica.” C. 
Muller, in his u Synopsis Muscorum,” has a. with rounded leaves, b. with 
truncate leaves, and the latter is again divided into two, according as the 
peduncular leaves have or have not spiral fibres. Sullivant, in Asa Gray’s 
“Botany of the Northern United States,” arranges the species by the relative 
positions of the two kinds of cells, seen on cross section of a leaf, a character 
far too minute and difficult to be observed to be of practical utility. Prof. 
Schimper places all the species in two groups, Monoicous and JDioicous ; also 
a most unpractical arrangement, as apart from the inconspicuous nature of 
the flowers, the species are so frequently found in a barren state, that such 
a mode of arranging them affords no help to the student. Lastly, Prof. 
Lindberg, in his paper which appeared in the “ Ofversigt K. Vetenskaps 
Akad. Forhandlingar ” for 1862, has, with a master’s hand, distributed the 
Sphagna in natural groups, characterised essentially by the form of the 
branch leaves, and leaving nothing to be desired. After separating S. ma- 
crophyllum as the genus Isocladus, Prof. Lindberg divides the Sphagna into 
two sections ; 1. Homophylla, having the stem leaves and branch leaves 
alike in form, and destitute of threads. S. sericeum and S. Holleanum from 
Java and Sumatra belong here. 2. Heterophylla , having the stem and 
branch leaves of different forms, and in this section four groups include the 
European species. In a letter recently received by Dr. Braithwaite, Prof. 
Lindberg alters the sequence of these, placing S. cymbifolium first, and this 
order is followed by the author in the paper referred to. 
The Terms JEndogen and Exogen . — At a meeting of the Royal Micro- 
scopical Society in January last, Professor T. Dyer dwelt upon the necessity 
of abandoning these terms in botanical language. He remarked that Pro- 
fessor Williamson’s recent proposal to introduce them into palaeontology 
was very objectionable. Our great English naturalist, John Ray, laid the 
foundations of a natural classification of flowering plants by dividing them 
into Dicotyledons and Monocotyledons. De Candolle thought these two 
groups might be characterised more conveniently by the mode of growth 
of their stem ; he substituted, therefore, for Ray’s names, those of exogens 
and endogens. It had, however, been shown that De Candolle’s views in- 
volved an entire misconception of the mode of growth. By the researches 
more especially of Mohl, it had been proved that Monocotyledons were 
really not endogenous at all ; they might, indeed, be more properly described 
as acrogenous. Then, again, exogenous growth was by no means confined 
to Dicotyledonous plants. Mr. Berkeley mentioned something very like it 
in a lichen ( Ipnea ). It was well known to occur in Lessonia, the great sea- 
weed of the southern oceans, and, according to Ruprecht, also in the allied 
Laminaria digitata of our own shores. In Draccena, an undoubted Mono- 
cotyledon, there were regular concentric zones of circumferential growth. 
