138 Gibson . — Contributions towards a Knowledge 
of species, and draws attention to the distinction to be made 
between the creeping and erect portions of the shoot-axis, 
a distinction which has been strangely lost sight of by later 
anatomists. Indeed, judging from the published papers, the 
creeping stems of some of the most important species, such as 
6'. spinosa , Braunii , S. inaequalifolia , and 5. Lyallii , seem 
never to have been sectionized at all. Spring remarks that 
the stem may contain one, two, four, or more vascular bundles, 
and adds that the so-called articulations on the erect stems of 
those species known as ‘ Articulatae ’ are due to hypertrophy 
of the cortex — the vascular system taking no part in their 
formation. The branching, according to Spring, is always 
dichotomous, a statement, however, which has not been con- 
firmed by later researches. The ‘ corps ligneux,’ always 
a multiple of two in number, is enveloped by a ‘ couche gene- 
ratrice ’ of cellular tissue, which Spring considers as destined to 
become on the one hand ‘ liber,’ on the other ‘ fibres ligneux.’ 
The £ couche generatrice ’ is surrounded by ‘ liber ’ composed 
of long thin-walled cells, and that in turn by an ‘ enveloppe 
herbacee,’ the cells of which contain chlorophyll, starch, &c., 
and an epidermis. Spring’s ‘ couche generatrice ’ would ap- 
parently correspond to what is now considered true phloem, 
the ‘liber’ being the so-called pericycle. No mention is 
made of the lacunae or of trabecular tissue ; but in all proba- 
bility Spring’s observations were made on herbarium material, 
under which circumstances the lacunae might possibly be set 
down to the effect of desiccation. 
Russow (11) states that the vascular bundles of Selaginella 
are built upon the fern-type, each consisting of one or more mar- 
ginal protoxylems and a centripetally developed metaxylem 
of scalariform tracheides, surrounded by one or more layers 
of parenchyma (Geleitzellen). These layers separate the wood 
from the phloem, which, he says, consists in greater part of 
a two to three-layered phloem-sheath, enclosing an incom- 
plete layer of proto-phloem.. No mention is made of sieve- 
tubes as such ; indeed, he expressly says, ‘ deutlich aus- 
gepragte Siebgefasse finden sich nur bei Equisetum und 
