MOSSES WITH A HAND-LENS 155 



■^ .jrj^ in length ; spores light yellowish-brown, 



jfjh,"" maturing in autumn. Widely distributed 



IS^ I "^^f l""' apparently not abundant. 



'^J .\'^Y '^'^^ Horned Liverworts are the highest 



"^Jhj^^ of the Bryophyta and by many are consid- 



^l-'%-.::M\ ^y^^ as the ancestors of the Perns, but they 



ySx'x^M I ^I'E P^it here for convenience, as they are 



ir\I sure to be sought with the other thalloid 



/// /s^' /} hepatics. 



MARCHANTIACEAE. 

 The True Liverworts* 



Figure 78, No- '^^^ plants of this family consist of a 



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



(After Sullivant.) gix inches in length, usually branching 



dichotomoLisly 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; gemmze in cup-shaped re- 

 ceptacles; capsule-bearing receptacles with 7 to 11 conspicuous 



rays Marchantia- 



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

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

 agonal Conocephalum. 



Thallu? less than two inches in length and much less than Yz 



inch in width 4. 



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

 receptacles which might be mistaken for gemmas-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 S 



