Z YCOPODINEA K. -HOMOSPOR US L ] 'CO PODIA CEAE. 277 



'I'he history of the development of the vegetative organs is only perfectly known 

 in our native Lycopodiaceae. There is no apical cell at the growing end of shoot, 

 leaf or root in Lycopodium. The growing point of the shoot is occupied by a 

 small-celled primary meristem, in which no differentiation into dermatogen and 

 periblem can be perceived, and the rudiment of the vascular bundle formed of 

 elongated cells comes nearly up to the apex of the shoot. In Z. Selago the apex is 

 flat, in Z. complanatu?n. L. clavatum, L. annotinum, Z. alpinum, and others it is convex 

 and rises above the youngest leaves. The leaves and the rudiments of new shoots 

 (bifurcations and brood-buds) are formed, as in the Phanerogams, not from single 

 cells of the growing point, but from groups of cells which embrace both the outer- 

 most and the deeper-lying layers of the tissue of the vegetative apex. 



The branching of the stem is partly monopodial, partly dichotomous, and there 

 are not a few cases where it is uncertain which of the two schemes more properly 

 applies. The branching of the vegetative shoots of Lycopodium clavatum, L. annotinum, 

 and Z. inundatufu is monopodial. In Z. clavatum, for instance, the rudiment of the 

 branch appears as a protuberance beneath the growing point of the primary axis, and 

 the protuberance is considerably smaller than the point itself. The branching in 

 this case has no relation to the leaves ; the rudiments of the branches are much 

 larger than the rudiments of the leaves, so that they are not placed in the axils of the 

 leaves, but above a number of them. On the axis of the spike of Z. alpinum there is 

 a bifurcation; the vegetative cone broadens out into two new growing points which 

 are formed right and left of it, and then ceases to grow itself ; while the two lateral 

 shoots develope as the prongs of the fork, the apex of the mother-shoot is suppressed. 

 A similar process takes place in the branching of Z. Selago according to Cramer, and 

 in die vegetative shoots of Z. complanatum and Z. C ha?Jiaecyparissus, two heterophyllous 

 species. Cramer states that in Z. Selago two new growing points of equal strength 

 appear side by side on the level surface of the apex, and develope in a forked 

 manner. 



Lycopodium complanatum and Z. Chamaecyparissus , which like the Selaginelleae 

 have their leaves in four rows, branch only in a plane which coincides with the plane of 

 the larger lateral leaves. The other species, in which the leaves are inserted spirally or 



laterally from the parent plant. Meanwhile an outgrowth appears on the opposite side of the axis 

 from that on which the tuber projects, and below the insertion of the oldest leaf : this is the first root. 

 It has been clearly proved by both external observation and by study ot sections, that the root in 

 Phylloglossuin is of exogenous origin. Among other known examples of this anomalous mode of 

 root development it is interesting to note the root of the embryo of Isoetes. In those cases where the 

 tuber is relatively laige, sporangia are formed ; these are, as is already known, borne upon an 

 elongated axis, which is the direct product of the apex of the tuber. A different origin is necessary 

 in this case for the tuber, and it has been found that the tuber originates in such plants in an 

 adventitious manner, as a depression at the base of the sporangium-beaiing axis or peduncle ; the 

 details of its development are otherwise similar in this case to that above described.' A comparison 

 of both external form and as far as possible of internal structure between Phylloglossum and the 

 young plants of Lycopodium cernuum, recently described by Treub (see note on page 275), 

 shows many points of striking similarity ; and Bower is led to the conclusion ' that provided tlie 

 oophore generation of Phylloglossum (which has never yet been observed) correspond in its more 

 important points to that of Lycopodium, we may regard Phylloglossum as a form which retains and 

 repeats in its sporophore generation the more prominent characteristics of the embryo as seen in 

 Lycopodium cernuum ; it is a permanently embryonic form of a Lycopodiaceous plant.'] 



