216 Wigglesworik . — The young Sporophytes of 
sometimes of considerable size (see i.s., PL XXII, Fig. 9). These air-spaces 
are apparently produced by the breaking down of the cortical cells ; they 
do not occur throughout the root. 
Air-spaces of any considerable size, formed by the breaking down of 
the cortical cells, are not of frequent occurrence in roots of terrestrial 
plants. According to Bower 1 air-spaces occur in the internal roots of 
L. Selago, where the outer cortex may be completely separated from the 
inner cortex by an air-space of schizogenetic origin. He also considers 
it probable that the outer air-space in Stigmarian rootlets was formed in 
the same way ; and considering the possible relationship of these forms, they 
may mark the retention of an ancestral character in the Lycopodiaceae 
from a more aquatic ancestry, though not necessarily from Lepidodendreae. 
(b) The second and following roots. The second and following roots 
arise endogenously in the apical region of the stem. Bruchmann 2 has 
studied the origin of the roots in the stems of the Lycopodiaceae, 
particularly in L. inundatum , and found that they arise endogenously in 
acropetal order from several layers in the cortex, on the ventral side of the 
stem. Fie figures a transverse section of the stem of L. clavatum showing 
the origin of the root in these layers. Van Tieghem and Douliot 3 , who 
also studied the origin of the roots of Lycopodiaceae, agreed with 
Bruchmann with regard to their endogenous origin, but came to a different 
conclusion as regards the exact layers of the stem which participate in their 
formation. They consider that the pericycle (pericambium) alone gives 
rise to the roots. 
The young sporophytes of L. clavaium show very clearly the endo- 
genous origin of the roots. One of those I examined, the stem of which 
was about 2 cms. long, showed no less than five rootlets which had not 
pushed their way out into the soil ; they appeared as masses of cells with 
dense protoplasmic contents and large nuclei in the inner cortex. The 
exact layers in which they originated could not be traced, as the apical 
portion of the stem, in which this must be looked for, was destroyed. 
Whilst agreeing in the absence of a primary root, the Lycopodia differ 
from Selaginella with respect to the origin of the roots, which in the 
latter, apparently, do not arise directly from the stem in the apical region, 
but are developed endogenously from exogenous organs (rhizophores), 
which are found at the base of the stem and at the bifurcations 4 . In this 
respect the condition in Selaginella might be regarded as intermediate 
between that of Lycopodium and Phylloglossmn , for in the latter the roots 
arise exogenously. 
1 Bower, On the Structure and Anatomy of the axis of Lepidostrobus Brozvnii . Annals of 
Botany, vol. vii, 1893, p. 331. 
2 Bruchmann, loc. cit , p. 75, and PL IV, Fig. 31. 
3 Van Tieghem and Douliot, Ann. des Sc. Nat., 7 e ser., T. viii, p. 553. 
4 Bruchmann, Untersuchungen iiber Selaginella spimilosa , 1897. 
