GROUP III. PTERIDOPHYTA : LYCOPODIX.E. 387 



margins of the shoots being larger than those on the flattened surfaces. 

 The leaves are sessile, simple, and have a rudimentary midrib. 



The sporophylls present considerable variety. _ In L. Selago and its 

 allies they are quite like the foliage-leaves ; in most species of Lycopodium 

 (e.g. L.inundatum, clacatum, Phlegmaria, etc.) the clearly differentiated 

 sporophylls are aggregated into terminal cone-like flowers, and in some 

 cases the branch bearing the cone grows out into a long peduncle (L. 

 dauatum, cotnplanatum, etc.). 



The sporangia are borne singly on the upper surface of the sporophylls 

 near their base. The archesporium consists of a single row or of a few 

 rows of cells which, by their division, give rise to the mother-cells of the 

 spores. The sporangia are unilocular, somewhat reniform in shape, and 

 (in Lycopodium) seated on a short broad stalk ; they dehisce by a longi- 

 tudinal slit. 



The spores are all of one kind, and are tetranedral in form ; they have 

 the ordinary structure. 



The roots are all adventitious. In the erect species of Lycopodium they 

 spring as a tuft from the basal end of the stem : in the procumbent species 

 they are born singly on the under surface of the stem. The roots branch 

 dichotomously in alternate planes. 



General Histology. The growing-point of stem and root alike consists, 

 in Lycopodium, of small-celled meristem, no apical cell being present. 

 Both stem and root have an axial vascular cylinder consisting of alter- 

 nating bundles of wood and of bast arranged radially (p. 125) : thus the stem 

 is monostelic, and its structure only differs from that of the stouter roots 

 in respect of the larger number of bundles present: in smaller roots there 

 is only one wood- and one bast-bundle. In the stem the bundles fre- 

 quently anastomose, more especially in the erect-growing species, so that 

 transverse sections taken at different levels present diverse pictures. The 

 wood-bundles consist of scalariform tracheids, with the exception of the 

 protoxylem. Neither stem nor root grows in thickness. In both stem 

 and root there is an endodermis, the cells of which have the characteristic 

 marking when young, but eventually become thick-walled and corky. 



The leaves of Lycopodium are of verj- simple structure ; they usually 

 have stomata on both surfaces. 



Embryogeny of the Sporophyte. The early stages have only been observed 

 in L. Phlegmaria, where the oospore is divided by a transverse basal wall, 

 the cell next to the neck of the archegonium being the hypobasal cell, 

 and the lower cell the epibasal. The hypobasal cell developes into a short, 

 cylindrical, usually unicellular, suspensor (p. 347). The somewhat hemi- 

 spherical epibasal cell becomes segmented into four octants "by two walls 

 at right angles to each other and to the basal wall ; and then the octants 

 are divided transversely, by a wall at right angles to the two preceding, 

 into two tiers or stages of four cells each. Of these two tiers the lower 

 forms a short hypocotyl (as in Salviuia, see p. 377) which is commonly (but 

 erroneously) called the foot, though it is morphologically quite different 

 from the foot of the Filicinse and Equisetinse. The upper tier of cells 

 gives rise to the first leaf or cotyledon, and to the primary stem. The 



