TYPES or CRYPTOGAMS ; BKYOPHYTES 



279 



Pig. 203. — Section tlirough Anther- 

 idial Keceptacle of Marchmitia. 

 (Magnified.) 



a, antheridium. 



337. Internal Structure. — Cut thin cross-sections of the thallus 

 in the same way as for Physcia, making some pass through the cir- 

 cular dots mentioned above. Exam- 

 ine under a high power and note the 

 different kinds and layers of cells 

 composing the thallus. Note the 

 character of the cells forming the 

 upper and lower surfaces. Describe 

 the cells which are next above those 

 of the lower epidermis, their shape, 

 color of contents, approximate num- 

 ber of horizontal rows. Have they 

 any evident intercellular spaces ? Find 

 cells connecting these with the upper 

 epidermis and constituting the net- 

 work of lines seen on the surface of 

 the thallus. Note the air cavity 



bounded by these lines and the loose cells which occupy it in part. 

 What is the color of their contents? How are they attached, and 

 how arranged? Can you discover any 

 opening through the epidermis? If so, 

 describe it. 



Make drawings to illustrate the details 

 of structure observed. 



338. GemmEB. — Look for a thallus 

 bearing little green cups formed of its 

 own substance. Describe the contents 

 of the cup. The bodies are called gemma. 

 They originate by vegetative growth alone 

 and when detached may grow into new 

 plants. 



339. Fruiting Organs. — Look for thalli 

 bearing stalks with umbrellarlike expan- 

 sions. The umbrellas are of two kinds, 

 one disk-like with crenate points (how 

 many?) and the other has rays (how many?) elongated and curving 

 downward. Is there any difference in the height of the two kinds ? 



az 



Ko. 204. — Sectional View of 

 an Antheridium of Mcvr- 

 chtmtia, 



a, antheridium ; az, anthero- 

 zoids, X 700. 



