MOSSES WITH A HAND-LENS 



153 



RICCIA. 



Two of our Riccias included here are readily recognized by 

 reason of their floating habit, in spite of the fact that the 

 capsules are rarely observed. 



R. PLUITANS L., the Slender Riccia, consists of a very thin 

 slender floating thallus, repeatedly forking (dichotoraous) and 

 often intertangled so as to form small mats. The thallus is very 

 narrow, yj to ^ inch in width and from J4 to 2 inches long. 

 Floating, it has no roothairs but it frequently is left on muddy 

 banks where it sends out numerous roothairs into the soil. 

 Rather rare. 



Figure 75. Riccia Huitans (After Bischoff.) P. Plants natural size. 

 Q. Portion of the thallus with fruit seen from above. R. The same seen 

 from below. S. Cross section of frond through imbedded capsule. 



RiCCiocARPUS NATANS (L.) Corda, the Purple-fringed Riccia, 

 is a very different looking plant with its branches obcordate or 

 wedge-shaped, ^ to J^ inch long and nearly as broad. There is a 

 strongly marked furrow along the middle of each branch and an 

 abundance of slender purplish scales underneath. The stomata 

 are large and easily seen with a hand-lens. Frequent in stagnant 

 ponds. 



