. The structure and development of mosses and ferns (Archegoniatae). o has made a compar-ative study of the subter-ranean and aerial stems ofP. jimiperiniim, dividesthe outer tissue of the lat-ter into epidermis, hypo-derma, and cortex. Inthe subterranean stems hefinds the constructionquite different from thatof the leafv section of the formeris triangular, and its epi-dermis provided withhairs which are absentfrom the epidermis of theaerial parts. Rudimen-tary scales, arranged inthree rows, are present,and corresponding tothese are strands of tissuethat represent the leaf-traces
. The structure and development of mosses and ferns (Archegoniatae). o has made a compar-ative study of the subter-ranean and aerial stems ofP. jimiperiniim, dividesthe outer tissue of the lat-ter into epidermis, hypo-derma, and cortex. Inthe subterranean stems hefinds the constructionquite different from thatof the leafv section of the formeris triangular, and its epi-dermis provided withhairs which are absentfrom the epidermis of theaerial parts. Rudimen-tary scales, arranged inthree rows, are present,and corresponding tothese are strands of tissuethat represent the leaf-traces of the aerial central cylinder ismuch larger relativelythan in the leafy branches,and its cross-section is notcontinuous, but is inter-rupted by three pericyclicsectors, composed ofcells whose walls are butlittle thickened. Thepoint of each sector is atthe periphery of the me-dulla, or central cylinder,and the broad end towardthe centre. As might beexpected, intermediate con-ditions are found wherethe rhizome begins to grow upward to form a leafy Fig. 121.—A, Transverse section of the leaf ofLeucohryum; B, similar section of the leaf ofPolytrichum commune; cl, chlorophyll-bear-ing cells (after Goebel). 224 MOSSES AND FERNS CHAP. The male inflorescence of the Polytrichaceae is especiallyconspicuous, as the leaves immediately surrounding the anther-idia are different both in form and colour from those of thestem. They are broad and membranaceous, and more or lessdistinctly reddish in colour. A well-known peculiarity ofthese forms is the fact that the growth of the stem is notstopped by the formation of antheridia, but after the latter haveall been formed the axis resumes its growth and assumes thecharacter of an ordinary leafy shoot. This, of course, indi-cates that, unlike most of the Mosses, the apical cell does notbecome transformed into an antheridium, and the researches of
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