VASCULAR CRYPTOGAMS 



by closed concentric ' vascular ' bundles, each surrounded by its bundle- 

 sheath, and the branching is always monopodial. The roots except in 

 Salvinia, which is rootless are fibrous, are furnished with a root-cap, 

 and branch monopodially. The leaves also vary greatly in form. In 

 Pilularia they are erect, cylindrical, and setiform : in Marsilea (L.) the 

 lamina consists of several distinct leaflets at the extremity of a more or 

 less elongated petiole. In both these genera the vernation is circinate. 

 In Azolla the leaves are deeply bifid. Salvinia is remarkably hetero- 

 phyllous. While the majority of the leaves retain an ordinary leaf-like 



habit, others develop into coriaceous 

 scutiform structures, while others again 

 divide into a number of capillary 

 segments, which perform the function 

 of roots, and at the same time bear the 

 non-sexual propagating organs. 



The fructification is of a more 

 complicated structure than in other 

 classes of Vascular Cryptogams. In 

 Salvinia it springs from the lower teeth 

 of the submerged leaves ; in Azolla 

 from the pendent section of the deeply 

 bipartite leaf, or rather of one particular 

 leaf; in Pilularia it stands beside and 

 beneath the leaves ; in Marsilea (L.) on 

 the under side of the petiole, or of the 

 base of the leaf itself. The Rhizo- 

 carpese are always monoecious, the two 

 kinds of sporange being produced on 

 the same individual, and usually in 

 close proximity. The structure and 

 degree of complexity of the fructifi- 

 cation differ in the different genera. 

 The sporanges are always associated 

 together in groups. Each of these groups, known as asorus or sporocarp, 

 is a closed capsule-like chamber, which is of epidermal or trichomic 

 origin, its w r all or indusium, often considerably hardened, being an 

 extension of the epiderm. Each sporocarp is regarded by Celakovsky 

 as the homologue of the integumented ovule of Flowering Plants. In 

 the Salviniaceae the sporocarp is unilocular; in the Marsileaceae it is 

 plurilocular, and the wall indurated into a hard shell. Each sporocarp 

 may contain sporanges of one kind only or of both kinds ; in the former 

 case male and female sporocarps are often associated together in 



FIG. 8. Salvinia natans L. Young 

 plant still attached to the prothal- 

 lium^r, and megaspore 5^. f>, scuti- 

 form leaf ; / and //, first and second 

 leaves ; L 1 and L", later aerial, and 

 iv, submerged leaf of the first whorl. 

 (After Pringsheim, x 20.) 



