434 



SYSTEMATIC BOTANY. 



Tig. 502. 



and archegonia are produced in cavities excavated in the thalloid stem ; 

 and from the archegonium springs a thread-like or pod-like capsule, which 

 splits down longitudinally into two valves when ripe, and displays a 

 central columetta, and has both spores and imperfect elaters. Illustrative 

 Genera : Metzgeria, Radd ; Blasia, Mich. ; Frullania, Nees ; Trichocolea, 

 Nees ; Geocalyx, Nees ; and Jungermannia, Dill. 



The MARCHANTIEJE, or Liverworts, are minute green plants, with 

 a stem in the form of a lobed, leaf-like, cellular expansion, rooting by 

 capillary filaments below, with an indistinct midrib ; the sporogonia de- 

 pending from the underside of a capitate or radiate receptacle supported 

 on a stalk arising from the apex, on the under surface, of the lobes of the 

 frond ; the capsules bursting by teeth or by irregular fissures, containing 

 elaters mixed with the spores, but no columella. 



The Thalloid Hepaticte have a broad, more 

 or less succulent, lobed, leaf-like expansion in 

 place of stem and leaf (fig. 502) ; this is to be 

 regarded as a foliaceously developed stem analo- 

 gous to that of Lemna among the Phanerogamia. 

 The sporogonia borne by the tlialloid forms are 

 very varied: the Pelliece, or frondose Jungerman- 

 nieae, bear capsules like those just described, but 

 arising from the midribs of the thalloid stem ; the 

 Anthoceroteae, Riccieae, and Marchantieae are very 

 different. 



The thalloid expansion of the Marchantiese 

 sends up stalk-like processes from its marginal 

 sinuses (fig. 502, A), terminating in simple or 

 divided cap-shaped bodies (receptacles), on the 

 underside of which are found the archegonia ; the 

 antheridia are in distinct heads ; the archegonia 

 develop into the capsules of the sporogonia (6), 

 which usually burst at the apex (c) into four teeth, 



sometimes into eight ; in certain genera a lid sepa- Organization of Marchan- 

 rates by transverse dehiscence, and in others the : ~ A ' Marchantm v~ 



capsule bursts irregularly ; the capsule has no colu- 

 mella, and its spores are mixed with elaters (d). 



The Marchantieae produce cellular bulbils or 

 gemmae. These are especially remarkable in some 

 of the thalloid forms, as in Marchantia, where 

 they are developed in groups in special cup-like 

 receptacles. 



The Marchantieae grow in damp shady situations in all climates. Illus- 

 trative Genera : Fegatella, Radd ; Plagiochasma, Lehni. j and Marchantia 

 March. 



The RICCIACE^; are inconspicuous Marchantia-liliQ Liverworts, o-rowiuo- 

 in mud or floating on water, having a delicate cellular leaf-like "frond,* 

 with the sporogonia, without an involucel or involucre, immersed in or 

 sessile on the frond, bursting irregularly, and containing no elaters. The 

 antheridia and archegonia are also imbedded in the substance of the 



tacle of fruit ; b, vertical 

 section of the receptacle, 

 showing the sporanges on 

 its under surface ; c, spo- 

 range bursting, with its 

 vaginule and perigone laid 

 open ; d, spores and elater, 

 highly magnified. 



