CRYPTOGAMS 



461 



constructed like those of the Ferns, but have a shorter neck, whose upper cells 

 become disorganised on opening. The number of neck-canal-cells differs in the 

 various species (1, 3, 5, or 6-10). 



The embryonic development agrees closely with that of Selayinella (Fig. 428). 

 A SUSPENSOR is developed ; it is not, however, laterally inserted, but occurs, on 

 the contrary, at the foot end of the embryo, or between the foot and the apex of 

 the stem. 



The spores of Lycopodium clavatum and other species are sometimes used in 

 pharmacy. 



Order 2. Selaginellaeeae ( 11<J ) 



To this order belongs the genus Selaginella, represented by numerous and for 

 the most part tropical species. They have, as a rule, profusely forked, creeping, 

 and sympodially branched stems, but occasionally erect, branched stems ; some 



A 



FIG. 424. A, Selaginella. helvetica (from 

 nature, mat. size). B, Selaffinella den- 

 ticulata, embryonic plant with macro- 

 spore still attached. (After BISCHOFF, 

 magnified.) 



FIG. 4-2J.Selaginella helvetica. A, macrospor- 

 anxium from above showing the line of dehis- 

 cence (d). B, opened, seen from the side ; tin- 

 four macrospores, C, have been ejected. /), 

 microsporangium in the axil of its sporophyll. 

 K, the same, opened. F, microspores. (x 

 about 15.) 



form moss-like beds of vegetation ; others, climbing on adjacent plants, possess 

 stems several metres long. In general the Selaginellas are similar in habit to the 

 Lycopodiums. They have small, scale-like leaves which usually exhibit a dorsi- 

 ventral arrangement, such as is shown, for example, in the alpine Selaginella 

 helvetica (Fig. 424), the stem of which bears two rows of small dorsal or upper 

 leaves, and opposite to them two rows of larger, ventral or under leaves. The 

 development of a small, membranous ligule at the base of the leaves, on their 

 dorsal side, is characteristic of the Selaginellas. The rhizophores( 120 ) are organs that 

 are peculiar to the plants of this order ; they are cylindrical, leafless, shoot-like 

 structures, which arise exogenously, usually in pairs, from the stem at a bifurcation 



