r j^fM^mE^ . 465 
subterranean shoots) three spiral rows of segments, the segmental walls advancing 
in the anodal direction, as in many Mosses. The small widely separated leaves, 
which have no fibro-vascular bundles, are borne upon the angles of the stem and bear 
no apparent relation to its branches. 
Psilotum iriquetruvi is a plant perfectly destitute of roots, forming however a 
number of underground shoots which serve the purpose of roots and are extremely 
similar to them. On the shoots of the rhizome which approach the surface of the 
ground may be detected with a lens minute leaves of a whitish colour and acicular 
shape ; the deeper root-like shoots have a blunter end, on which no trace of leaves 
can be detected, even with the lens. While the anatomical structure of the super- 
ficial shoots corresponds to that of the true stem of these plants, in these deeper 
shoots the vascular bundles are united into an axial group, as in true roots. The 
shoots which bear visible rudiments of leaves may turn upwards, become green and 
transformed into ordinary foliage-shoots, while the root-like shoots, which are more 
slender, may also turn upwards, become thicker, and assume the appearance of 
the ordinary superficial rhizome-shoots. In this point therefore they differ at once 
from true roots, but still more in the absence of a root-cap. They terminate in an 
apical cell, which forms oblique segments alternating in different directions. The 
most important point, however, is that these shoots really possess rudiments of leaves 
which consist of only a few cells and do not project above the surface, but remain 
concealed in the tissue. They are best recognised in longitudinal section, when 
they are seen to consist of an apical cell and from two to five cells with the 
characteristic arrangement of leaf-cells. Similar rudimentary leaves consisting of 
but few cells occur also on the ordinary rhizome-shoots, where, however, they do 
not undergo further development, especially when the end of the shoot appears 
above ground. The root-like shoots branch like the ordinary ones ; a cell is cut 
off by an oblique wall from one of the youngest segments, and forms the apical 
cell of the new shoot. 
The other genera all possess true roots. In the Lycopodieee with creeping 
or climbing stems they arise singly and dichotomise in rectangularly intersecting 
planes in the soil. It has already been mentioned that in the Lycopodiese witti 
erect stems, such as in Z. Selago^ Phlegmaria, ulicifolium, the roots issue in a tuft 
from the base of the stem which is somewhat tubercular. These roots originate high 
up in the stem, as high as five centimetres and even above the first bifurcation 
according to Strasburger ; they develope at the periphery of the axial fibro-vascular 
mass, but they are peculiar in that they grow down through the fundamental tissue of 
the stem and even dichotomise there. (Compare with Angiopieris, p. 417.) 
The Sporangia, in the genus Lycopodnwi, occur singly on the bases of the 
leaves or in their axils. As in all Dichotomeae, they are here larger than in the 
Ferns. They are borne on short broad stalks, and the capsule is somewhat reniform, 
its longer axis lying transversely to that of the leaf. They open by means of a slit 
running in this direction over the apex, tw^o valves being formed which remained 
united at the base. The contained spheroidal or tetrahedral rather small spores are 
numerous ; they all have the same shape and are provided with a sculptured exospore. 
After I had pointed out in the first edition of this book (1868) that the sporangia of 
the Lycopodiese originate as multicellular protuberances of the tissue of the leaves, 
H h 
