702 JUNGERMANNIACEJE. (SC ALE-MOSSES.) 



Subclass II. CELLULAK ACROGENS, or 

 BRYOPHYTES. 



Plants composed of cellular tissue only. Antheridia or 

 archegonia, or both, formed upon the stem or branches of the 

 plant itself, which is developed from the germinating spore 

 usually with the intervention of a filiform or conferva-like 

 prothallus. — Divided into the 3Iusci, or Mosses, and the He- 

 paticce. 



Division I. HEPATIC/E.^ (Liverworts.) 



Plants usually procumbent, consisting of a simple thallus, a 

 thalloid stem, or a leafy axis; leaves when present 2-ranked, 

 with uniform leaf -cells and no midvein ; thalloid forms with 

 or without a midvein, smooth or scurfy or scaly beneath and 

 usually with numerous rootlets. Sexual reproduction by aij- 

 theridia and archegonia, which are immersed in the thallus, 

 or sessile or pedicelled upon it, or borne on a peduncled re- 

 ceptacle. The fertilized archegonium develops into a capsule 

 {sporogonium) closely invested by a calyptra, which ruptures 

 above as the ripened capsule (containing numerous spores and 

 usually elaters) pushes upward. It is also commonly sur- 

 rounded by a usually double involucre, the inner (often called 

 perianth) more or less tubular, the outer tubular or more often 

 foliaceous, sometimes wholly wanting. Propagation is also 

 effected by offshoots {innovations), runners {flagella), or by 

 gemmoe, which appear at the margin of the leaves or on the 

 surface of the thallus, often in special receptacles. 



Order 137. JUNGEKMA]S:N'IACE.^. Scale-Mosses. 



Plant-body a leafy axis or rarely thallose. Capsule borne on a slender 

 often elongated pedicel, splitting at maturity into 4 valves. Elaters 

 mixed with the spores, mostly bispiral (unispiral in n. 1-3, 32, and 33, 

 1-3-spiral in n. 5 and 28). Antheridia and archegonia dioecious or 

 monoecious, in the latter case either mingled in the same inflorescence, 

 or separated upon the same branch, with the antheridia naked in the 

 axils of the lower leaves, or on separate parts of the same plant. Leaves 



1 Elaborated for this edition by Prof. L. M. Underwood, of Syracuse, N. Y. 



