366 



BOTANY. 



into four cells (C, Fig. 250), and from these the young plant 

 of the asexual generatinn is developed. The young plant is 

 quite simple, having small internodes, bearing sheaths which 



contain but three leaves ; lar- 

 ger shoots soon arise, with lar- 

 ger internodes and sheaths hav- 

 ing more leaves, and these are 

 followed by others still larger, 

 until at last the full size is 

 reached. 



479. — The spores of the 

 Equisetinee are produced either 

 upon the ordinary green stems, 

 as in Equisetum limosum and 

 JS. Jiyemale, or upon colorless 

 or brownish stems, which de- 

 velop early, and, after bearing 

 the spores, die and disappear, 

 as in E. Tehnateia and E. 

 arvense. The sporangia are 

 developed upon modified 

 leaves, upon the ends of the 

 stems. The spore - bearing 

 leaves, like the ordinary ones, 

 are in whorls ; each leaf is, 

 however, peltate in form, and 

 borne upon a short stalk (st, 

 Fig. 251, B). These peltate 

 leaves (usually called the pel- 

 tate scales) are collected into 

 cone-shaped clusters, and by 

 their mutual pressure eacla 

 scale becomes more or less 

 hexagonal in outline. Upon 

 the under surface of each scale 

 there arise five to nine or ten 

 cellular masses, which enlarge and become sac-shaped spo- 

 rangia ; certain inner cells become spore mother-cells, and 

 from each of these four spherical spores are produced. The 



Pig. 351. — Equisetum Telmateia. A^ 

 upper part of a fertile stem, with lower 

 half ot the spike (nat. size) ; 6, sheath of 

 united leaves ; a, annulus or ring form- 

 ed of imperfectly developed leaves ; x, 

 the pedicels of peltate scales which have 

 been cut off ; y, section of the rachis of 

 the spike. B^ peltate scales, s, s, in 

 various positions (slightly magnified) ; 

 «(7,the sporangia borne on tiic under side 

 of the scales ; si, at, the pedicels of the 

 -After Sachs. 



