28 MR. C, E. JONES ON THE MORPHOLOGY 
a very primitive type. Without going so far as to assert that the root-structure has 
remained unaltered throughout tbe range of vascular Cryptogams and Phanerogams, it 
appears that the arrangement which served for Lycopods, both in stem and root, has 
proved to be suited to roots generally. But as soon as the structure of the vascular 
cylinder in Lycopods begins to get complex, even in young plants, there is a notable 
difference, because the disposition of the different elements is constantly changing; even 
if the protoxylems remain constant in number, the positions are constantly shifting, and 
the phloem-inlets spread out into bands, or vice versá, and cross-connections between 
different xylem-bands are formed. It is presumed that the complex structure found in 
L. cernuum and L. salakense is the outcome of more irregular development and con- 
sequent interspersal of numerous small patches of phloem through the xylem. Exami- 
nations of serial sections have been made in order to get exact measurements of the 
changes which take place. In the stem of Z. clavatum a U-shaped patch of xylem on 
the dorsal side was found to remain unchanged throughout a distance of 1°5 em.; a 
definite phloem-inlet could be noted for a length of 1:8 cm., but for about 6 mm. it 
joined into a V curve with another inlet ; a small patch, consisting mainly of protoxylems, 
remained separate for a distance of 1 em.; other laterally situated portions of the xylem 
were observed to run for distances of 7 and 8 mm. before they joined up with the central 
mastof xylem. The stem of Z. squarrosum lends itself to a determination of this kind. 
Eight figures (Pl. 5. figs. 37-44) are shown, of which the distance between the first and 
last was 25 em. The number of protoxylems remains fairly constant, being for the 
most part sixteen, except in one section, where it has increased to seventeen, but they 
are constantly changing their positions. A phloem-island (p,), which is evident iu four 
sections, remains isolated for more than 1 em. and then joins up to phloem nearer the 
periphery, aud later becomes isolated again; the portion of phloem (p,), though not 
isolated, remains tolerably fixed in position and definite through a length of 6mm. The 
horseshoe-shaped mass of xylem (2), isolated in figs. 39 and 40, can be distinguished in  . 
four sections for a distance of 1 em. The portion of xylem (2) remains separated for a E 
similar distance. It is also instructive to observe how the directions of the phloem-areas | 
change. In fig. 37 the phloem is continuous on a line which makes a slight angle 
VN the horizontal, but it is not again renewed in this direction. A peculiar phase of 
Sonny is that shown in fig. 44, where it assumes the shape of a 7. The conclusions 
to be drawn from these measurements are that the most definite phases may persist from 
1-15 von and others Tor shorter distances; but it is more apparent that gradual changes 
are constantly occurring, since the strands seldom run vertically and the different parts 
are alternately joining up and separating. 
Roots.—The structure of the roots has not b 
as they were found running through the stems 
squarrosum. It is noticeable, in contrast with 
bundles of these roots and their orient 
een critically examined, except in so far 
of such species as Z. Selago, serratum, and 
the vascular cylinder of the stem, that the - 
ation remain nearly constant, A very large 
Pipes: of the roots are alike, and show the structure which is represented in fig. 36. 
cular system of the root connects up with two xylems and the intervening 
