422 PART III. THE CLASSIFICATION OF PLANTS. 



clavatum, 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. clavatum, complanatum, etc.). 



ID Phylloglossum the small sporophylls are aggregated into a cone borne ter- 

 minally on a peduncle which grows from the apex of the tuber : the lower 

 sporophylls only are fertile. 



The sporangia are, in both genera, borne singly on the upper surface of the 

 sporophylls near their base. The archesporium consists of a single row (L. 

 Selago, Phylloglossum) or of a few rows (I. clavatum) 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 longitudinal slit. 



arcTv. 



proth. 



-tub 



FIG. 275. Embryogeny of Lycor odium cernuum (x 300: after Treub). The embryo is 

 just emerging from the prothallium proth. ; arch, the neck of the archegonium ; I-I basal 

 wall; susp. suepensor; cot. cotyledon; tub. tuberous protocorm. 



The spores are all of one kind, and are tetrahedral in form : they have the 

 ordinary structure. 



The roots are all adventitious. In the erect species of Lycopodiam 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 dichoto- 

 monsly in alternate planes. In Phylloglossum the short unbranched roots 

 (1-3) spring from the tuber just below the insertion of the leaves : they are of 

 exogenous origin. 



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

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



