CRYPTOGAMS 335 
a true root? Notice that as the lower end dies, the growing 
branches go on increasing and reproducing the thallus. 
Do you find anything like a midrib? If so, trace it through 
the branches and body of the thallus; where does it end? 
Does it seem to be formed like the midrib of a leaf? Hold 
475 476 
Fies. 475, 476. — Umbrella liverwort (Marchantia polymorpha) : 475, portion of a 
female thallus about natural size, showing dichotomous branching ; f, f, archegonial 
or female receptacles ; 7, rhizoids ; 476, portion of a male thallus bearing an anther- 
idial disk or receptacle, d, and gemma, g, g. 
a piece of the thallus up to the light and see if you can detect 
any veins. Is it of the same color in all parts, and if there is 
a, difference, can you give a reason for it? Examine the 
upper surface with a lens. Peel off a piece of the epidermis, 
place it under a low power of the microscope, or between 
two moistened bits of glass, and hold up to the light, keeping 
the upper surface toward you; what is its appearance? 
