350 



BOTANY. 



takes place simply by the decay of the sporogonium ; in 

 Anthoceros the long sporogonium splits 

 vertically into two long valves (Fig. 

 239), while in the greater part of the 

 class it splits regularly 

 into a definite number 

 (four to six) of recurv- 



ing segments ; in the 



Fig 239. Plant of An- latter the elaters, which 



rSr^orogofia^un 6 are present, doubtless 



opened ; K, on the left, j Boffina- 4- V. a 

 Pporogoniaopened.-After aia m Setting tne 



spores free. The struc- 

 ture and development of the elaters are 

 shown in Fig. 240. 



The following are the principal orders of the 

 Hepaticae : 



Order Ricciaceae. Consisting of terrestrial or 

 aquatic annual plants of small size ; the plant- 

 body is a dichotomously branched thalloid stem, 

 which bears a row of scale-like leaves upon the 

 under side. The sexual organs occur singly on the 

 upper side of the stem, and the sessile, spherical 

 sporogonia (capsules) are immersed in it or sessile 

 upon it ; the capsule breaks irregularly upon the 

 decay of its walls ; and there are neither perianth 

 nor elaters. 



Order Anthoceroteas. Terrestrial annual 

 plants with an irregularly branched thallus. The 

 sexual organs are imbedded in the upper surface 

 of the frond, and are of very simple structure ; the 

 sporogonia are long and narrow, and dehisce by of development. The 

 splitting into two valves ; perianth none ; and the tobe'a^efon^ate^ell 

 elaters, when present, imperfect and rudimentary, with no trace ^as^yet 



Order Marchantiaceae. Terrestrial perennial 

 plants, with a thick, creeping, and dichotomously 

 branched stem, furnished beneath with numerous 

 scale-like leaves and root-hairs ; above, the stem is 

 provided with a well-developed epidermis, and pe- 

 culiar stomata of a complex structure, communi- h 

 eating with lozenge-shaped cavities (Figs. 78 and A, A, are mature 

 79, pp. 91-2). The sexual organs are developed on fP r r s ulSuSttrt 

 special erect branches, and they may occur on the Decaisne. 

 same, or on distinct plants ; the sterile or antheridial branches, which 



240. Two ela- 

 different stages 



are several youm; 

 right is mature. It 



tions of the wall, the 



