DIRECTIONS FOR LABORATORY STUDY. 377 



4. Occupying the central region on the upper surface, the 

 round colored disks, apothecia. Compare the form of the younger 

 ones nearer the margin. What change occurs as they grow 

 older? (^ 317, fig. 225.) 



5. Here and there, minute black specks, the mouths of sacs 

 sunk in the thallus, called spermogonia. 



Cut a vertical section through an apothecium and a part of the 

 thallus on each side. Observe 



6. The layers of the thallus; above and below, dense layers, the 

 upper and lower cortical layers; between them, the medullary 

 layer, with green alga: distributed unequally through it. 



7. The form of the apothecium : its broad short stalk and 

 rim; the convex surface of the disk. Is this more convex than 

 before cutting ? How shown ? Why ? 



S. The layers of the apothecium; the upper {hymenium) of ver- 

 tical parallel sporangia containing rows of black dots, the spores ; 

 the second {siib-hy?nenium) of fine, pale, tangled hyphae; the third 

 {itiediillary layer) with green algce; the lower cortical layer. {Fig. 

 226 ) 



9. Demonstration. In a very thin vertical section of apothe- 

 cium show the sporangia (asci) and ascospores; the paraphyses. 



10. Compare apothecium with the cup of Peziza. How are 

 they different? Do these differences seem important? (Figs. 

 222, 226.) 



F. MUSHROOM {Agaricus sp.). 



1. The mycelium of this plant consists of rope- or ribbon-like 

 strands of hyph« ramifying extensively in the substratum. The 

 fructification only is here studied (T| 314). Examine this part 

 fresh or in water. Observe in a mature one the two parts, stalk 

 and cap. (Fig. 216.) 



2. With a sharp long-bladed knife or razor cut the cap and 

 stalk lengthwise through center. Is the stalk hollow through- 

 out? Or is the central part only of different texture from outer? 

 Determine differences of texture by teasing apart the hyphae with 

 needles. 



3. Cut off stalk close under the cap. Turn the latter under side 

 up. Observe the radial plates (gills) extending from margin to 

 stalk. Do all reach the stalk ? 



4. Examine the young fructifications. By cutting them length- 

 wise observe the formation of the chamber from whose roof the 



