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 Uke 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 



Figs. 475, 476. — UmbrolUi liverwort (Mnrchnnlia polymorphn) : 475, portion of a 

 female thallus about natural size, showing dichotomous branching ; /, /, archegonial 

 or female receptacles ; r, rhizoids ; 476, portion of a male thallus bearing an anther- 

 idial disk or receptacle, d, and gemmaj, 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? 



