Lycopodium complanatum and Lycopodium clavatum. 217 
The second and following roots of the young sporophytes of 
L. complanatum and L. clavatum show a diarch arrangement at their 
base and throughout the greater part of their length, similar to that shown 
in PL XXII, Fig. 3, while after dichotomy the arrangement may be 
monarch. The two strands of xylem connect up with two tracheid groups 
of the stem as shown in PL XXII, Fig. 11. The growth of these roots 
appears to be retarded at first, and, as mentioned above, a whole row of 
young rootlets which have not grown out beyond the inner layers of the 
cortex may be seen in the young sporophyte. When favourable conditions 
for their development arise they push their way out through the cortex, 
generally more or less at right angles to the stele of the stem. Fig. 10 
shows one of these young rootlets in the stem of L. complanatum just above 
the foot region. 
The older sporophyte of L. clavatum was interesting, as it showed a 
rootlet which had travelled for some distance down the cortex of the stem 
(rt. y PL XXII, P'ig. 4) almost parallel with the axis, instead of pushing its 
way directly to the periphery, and in this respect it resembles the upright 
L . Selago and such forms as L. serratum, L. tetragonum , L. reflex uni, 
L. squarrosum , in which the occurrence of rootlets running through the 
cortex have been recently noted by Jones 1 . Referring to the rootlets in 
L. serratum , Jones 2 says that if the stem is growing quite erect the roots 
do not pass out, but gradually die out, and that only when the stem is 
growing obliquely do the roots emerge. The lower part of the stem of the 
young sporophyte of L. clavatum which contained the rootlet running down 
the cortex was bent at frequent intervals, and possibly the part in which the 
rootlet occurred was running in an almost upright direction, and this might 
partly account for its direction. It arose a short distance above the foot, and 
was the third root, in point of age, proceeding from the stem. The second 
and fourth roots grew more or less at right angles to the stem. The roots 
seem to be strongly geotropic, although in some cases other forces, possibly 
moisture and chemical attraction of other substances in the soil, act more 
strongly than gravity, and cause them to grow in a different direction. 
With regard to the internal structure of the rootlet in question, the 
differentiation of the vascular elements had begun ; two curved rows of 
narrow tracheides were discernible separated by thin-walled cells, some of 
which by their large size and absence of contents indicated metaxylem. 
The two groups of xylem elements were connected up with two groups of 
tracheides in the main axis (see PL XXII, Fig. 11), and in this respect 
resembled the roots running through the cortex of adult forms previously 
described. In the latter the two xylems usually join up, forming a crescent- 
shaped mass with small protoxylem elements at the tips of the crescent, but 
this is not always the case, for in a short piece of stem of L. dichotomum 
1 Jones, loc. cit., pp. 22, 23, and 24. 2 Jones, loc. cit., p. 22. 
