316 HEPATICJE. PAET n. 



SECTION YI. 



HEPATIOE, OR LIVERWORTS. 



THE Hepaticse are the small herbaceous plants, which 

 constitute the three distinct natural orders called re- 

 spectively Ricciacese, Marchantiaceae, and Jungerman- 

 niacese. They are distinguished primarily by the first 

 having the sporangia valveless, without elaters ; by the 

 second having dependent valvate or irregularly bursting 

 sporangia ; and by the third having the sporangia val- 

 vate and erect. Both the latter, moreover, have the 

 spores mixed with elaters. 



The Ricciacese, popularly called Crystalworts, which 

 form the lowest grade of Hepaticse, are inconspicuous 

 plants, growing in mud, or floating on water. They 

 have spreading, horizontal fronds, of a delicate cellular 

 structure and of indefinite form. Their fructification 

 consists of valveless spherical sporangia, or spore sacs, 

 imbedded in the frond ; cells are formed within these 

 sporangia, each of which cells is divided into four parts, 

 which become spores, and, when ripe, the surface of the 

 sporangia is fractured to give them egress. In some 

 species there are many air passages in the cavities 

 where the sporangia are produced. The under- surface 

 of the frond is often beset with scales. The genus 

 Biella differs from all the other genera in having an 

 upright branchless stem with a distinct wing or limb 

 forming a continuous spiral round it. In the male 

 plant, the edge of the frond bears the antheridia con- 



