INTRODUCTION TO CRYPTOGAMIC BOTANY. 433 



attended by curious appendages and stipules, while the colour 

 far more frequently assumes a purple hue, which is, however, 

 not confined to the foliiferous species. There is a peculiar 

 aspect about them by which they are known at once, except in 

 a very few cases, and the slightest experience is sufficient even 

 in these to prevent much hesitation. 



I. RicciACE^, Endl., Lindl. 



EicciEi, Nees ah Esenb.* Bischoff, Lindenb., &c. 



Sporangia valveless, sunk in the substance of the frond, 

 or raised above its surface ; surrounded by or adnate with 

 the calyptra, with or without additional envelopes, ultimately 

 bursting irregularly, and producing numerous spores without 

 elaters. 



478. The characters of this group are many of them nega- 

 tive, but the valveless sporangia, whether raised above the 

 surface or buried beneath it, taken in conjunction with the 

 constant absence of elaters, will always sufficiently indicate its 

 members. The simplest species belong to the genus Riccia 

 (Fig. 89, a, b), which exhibit a horizontal, more or less dichoto- 

 mous, lichenoid frond, which often appears like some Endocar- 

 pon or barren Jungermannia. The fruit, which consists of a 

 spherical sac filled with spores, is sunk into the substance of the 

 frond, in consequence of which the resemblance to an Endo- 

 carpon is still stronger. But the mode of origination of the 

 spores is totally different : in Riccia they arise from the 

 repeated division of mother cells, exactly after the fashion of 

 pollen grains, whereas in Endocarpon the sporidia are gene- 

 rated without cell-division from the protoplasm of the asc 

 (Fig. 82, c). There is, therefore, no affinity whatever, though 

 the external resemblance is so strong. They differ, more- 

 over, materially, in having a distinct axis of growth, which 

 exists in no foliaceous Lichen, and in the presence of air pas- 

 sages beneath the porous outer surface in some species, as in 



* In all that relates to HeiDaticce, I have to acknowledge my obli- 

 gations to the Synopsis Hepaticarum of Gottsche, Lindenberg, and 

 Nees von Esenbeck. 



