Z YCOPODINEA E. — LIGULA TA E. 29 1 



seen in the embryo (Fig. 232); it is not till later that we find a two-sided cell at the 

 apex, as in the primary axis. The branching in this species, as in all the Selaginelleae 

 which have been examined, is not dichotomous but lateral monopodial. The rudiments 

 of the leaves too are formed as in the genus Lycopodmm, two or more outer cells of 

 the growing point of the stem arching outwards and giving rise to the surface of the leaf. 



The roots. The species of the genus Selaginella have all true roots ; but in 

 some species, as S. Afartetisii and 6". Kraussiana, they are formed on a structure 

 which has the external appearance of a root but has no root-cap, and which Nageli 

 calls the rhizophore. In S. Kraussiana the rhizophores spring from the dorsal side 

 of the stem close to the base of a branch, bend round and then grow downwards; 

 it is unusual for two of these organs to be formed near each other. S. Mariensii on 

 the other hand forms the rudiments of two rhizophores at every place where a branch 

 is formed, one on the dorsal and one on the ventral side, the plane of which crosses 

 the plane of branching ; but usually the one only on the ventral side developes, the 

 other remaining as a small prominence. The rhizophores arise very near the growing 

 point, and later than the lateral branches near which they are placed ; their mode of 

 formation is the same as that of the branches. After growth has ceased at the apex, 

 the rhizophore which is still very short swells into a round shape, the walls of its cells 

 thicken, and the rudiments of true roots are at once formed inside the swollen part ; 

 the young roots however do not break through till the rhizophore has elongated 

 sufficiently by intercalary growth for its swollen extremity to bury itself in the ground, 

 where its cells become disorganised and deliquesce into a homogeneous mucilage, 

 through which the true roots grow out into the ground. Pfeffer has shown in the 

 case of S. Martensii, S. inaeqtialifolia, and S. laevigata that the rhizophores may be 

 transformed into true leafy shoots, which show some abnormalities of structure 

 in the first leaves, but afterwards develope like normal shoots and even form sporan- 

 giferous spikes. 



There are no rhizophores in S. cuspidata; in this species roots grow difectly 

 from the points nearest to the ground where the stem branches, and like the rhizo- 

 phores of S. Martensii branch before they reach the ground ; these roots also begin 

 to be formed very early near the growing point of the stem. Both these roots which 

 come immediately from the stem and those formed from rhizophores branch mono- 

 podially, and the successive planes of branching cross one another. The branches 

 appear very quickly one after another, and may be seen crowded together at the 

 extremity of the parent-root; the apical cell is tetrahedral (a three-sided pyramid), 

 as in the roots of Ferns and the Equisetaceae ; it soon ceases to give off segments. 

 and consequently the elongation of the branches is due almost entirely to intercalary 

 growth. The roots which emerge from the furrows in the stem of Isoetcs bifurcate 

 three or four times in planes which cross at a right angle, and they have no apical 

 cell ; the arrangement of the cells in the growing point agrees with that in the roots 

 of many Spermaphytes (Phanerogams). 



The sporangia of the Ligulatae are large in comparison with the size of the 

 leaves, and have short thick stalks. Each sporophyll bears one sporangium, which is 

 always placed below the ligule on the leaf in Isoetes, or above the leaf and on the stem 

 in Selaginella. 



In Selaginella the sporangia are shortl} stalked roundish capsules. The 



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