MOSSES WITH A HAND-LENS 



155 



in length ; spores light yellowish-brown, 

 maturing in autumn. Widely distributed 

 but apparently not abundant. 



The Horned Liverworts are the highest 

 of the Bryophyta and by many are consid- 

 ered as the ancestors of the Ferns, but they 

 are put here for convenience, as they are 

 sure to be sought with the other thalloid 

 hepatics. 



MARCH AN TI ACE AE. 

 The True Liverworts. 



FIGURE 78. No- The plants of this family consist of a 



tothylas orbicurlaris thallus of medium to large size, one-half to 



(After Sullivant.) s j x inches in length, usually branching 



dichotomously but sometimes with more 



than two branches at a fork. They are attached to the substratum 

 by numerous roothairs and are thickened in the middle to form 

 a midrib. This in some cases is not very apparent above but 

 shows plainly underneath. The upper surface is covered with 

 small pores (stomata) which are very apparent with a lens, 

 except in Reboulia. The capsules are spherical or ovoid and 

 open irregularly by imperfect valves or by a portion of the top 

 coming off after the manner of a lid. In this family the capsules 

 and usually the antheridia are borne on special long-stalked 

 receptacles well illustrated by the familiar Marchantia. 



KEY TO THE GENERA. 



1. Sterile stems bearing abundant gemmae in shallow open receptacles ... 2 

 Sterile stems without gemmae 3 



2. Found only in and around greenhouses; gemmae in crescent- 

 shaped receptacles; never fruiting in our region Lunularia. 



Growing abundantly everywhere; gemmae in cup-shaped re- 

 ceptacles; capsule-bearing receptacles with 7 to n conspicuous 



rays Marchantia. 



3. Thallus large; 2 to 6 inches long and */2 inch or more wide, dis- 

 tinctly areolate as in Marchantia, but areolae larger and hex- 

 agonal Conocephalum. 



Thallus less than two inches in length and much less than ^ 



inch in width 4 



4. Pores (stomata) scarcely distinguishable; antheridia in sessile 

 receptacles which might be mistaken for gemmae-bearing cups; 

 thallus purple on the margins; midrib strong underneath but not 



conspicuous above Reboulia. 



Pores conspicuous, white; antheridia in peduncled disk-like re- 

 ceptacles; thallus with numerous dark purple scales under- 

 neath Preissia. 



Pores conspicuous; antheridia immersed in the thallus; thallus 



purple underneath, at least along the margins 5 



