462 



KOTANY 



(cf. p. 50). At their ends a number of endogenous roots are produced, but the 

 rhizophores are able, when the normal shoots are cut back, to continue their 

 growth as shoots of ordinary construction. Even below the first leaves of the 

 seedling plant short rhizopliores are formed, from which the first roots arise 

 endogenoiisly. In many species of Sclaginella the epidermal assimilatory cells of 

 the leaves possess, as in Anthoceros, only one large chloroplast ( m ). 



As in Lycopodium, the cones or flowers are terminal. Each sporophyll 

 subtends only one sporangium, which springs from the stem above the leaf-axil. 

 The same spike bears both macrosporaugia and microsporangia. Each macro- 

 sporangium (Fig. 425 A-C) contains only four macrospores, which are produced 

 by the growth and division of a single spore-mother-cell ; all the other mother- 

 cells originally developed ultimately disappear. On account of the increasing size 



Klo. 4-26. A-E, Selugiitdla stolonijera, successive .stages in the ^ermiiiation of a Imicrospore.; 

 p, prothalliuin-cell ; if, wall-cells of aiitheridium ; .-. six>rmatogenous cells ; A, B, D, lateral, 

 C, dorsal view. In E the prothal Hum-cell is not visible, the disorganised wall-cells enclose 

 the spermatozoid mother-cells ; 7-". ipermttOBOid* ot'lSel"'.ii it'll" i-n*i>iilutii. (After HELAJEKK. 

 A-K x 640, F X 780.)- 



of the spores. the spherical macrosporaugia become nodular. Opening occurs along 

 definite lines of dehiscence, the wall splitting into two valves, which curve back 

 from a boat-shaped basal portion. The spores are ejected by the pressure of the 

 contracting boat-shaped part and the valves. Numerous spores are formed in the 

 flattened microsporangia. The mode of dehiscence is similar in these also, but the 

 boat-shaped portion of the wall is smaller, the valves extending to the base. 



The microspores begin their development while still enclosed within the 

 sporangium. The spore first divides into a small lenticular vegetative cell, which 

 corresponds to the rhizoid cell of Salvinia, and into a large cell, which divides 

 successively into eight sterile peripheral cells and two or four central sperma- 

 togenous cells (Fig. 426 A). By the further division of the central cells numerous 

 spermatozoid mother-cells are formed (B-D). The peripheral cells then break 

 down and give rise to a mucilaginous substance, in which is embedded the central 

 mass of spermatozoid mother-cells (E). The small prothallium-cell, however, 

 persists. Eventually the wall ruptures, and the mother-cells, thus liberated, 

 set free the club-shaped biciliate spermatozoids (F). The reduction here exhibited 



