and Laboratory Methods. 2521 



4. Examine the lower or ventral side of a branch under dissecting micro- 

 scope and note the semicircular ventral scales. Look for rhizoids. Mount one 

 of the ventral scales and draw under low power. 



Sporophyte. 



5. Examine a frond containing little yellowish, club-shaped bodies. These 

 are the sporophytes. Carefully pick out one which has the capsule unbroken 

 and one which shows the wall of the capsule split into four valves. Mount in 

 water and draw both under low power, showing the capsule, the foot and the 

 stalk. 



6. Draw a spore and an elater under high power, 



7. Compare the thallus of Porella with that of Marchantia, noting especially 

 the different ways in which the two thalli have been specialized for the work 

 of photosynthesis. 



XLVIII. Sphagnum cymbifolium (Ehrb.) Hedw. 



Class, Sphagna. Order, Sphagnales. Family, Sphagnaceae. 



The peat or bog mosses grow in and near water in swamps, bogs, and other 

 wet places. The species named above is unisexual, the male plant being more 

 slender than the female. 



Gametop/iyfe. 



1. Take a small mass of dry spagnum, soak it in water and notice the enor- 

 mous quantity it will absorb. 



2. Make sketches of a male and a female frond. Notice that the frond 

 keeps growing at the top and dying below. 



3. Sketch a branch under low power, showing the arrangement of the scales. 

 Draw a single scale. Is there any costa (midrib) ? 



4. Under high power draw a patch of cells from a scale, some with chloro- 

 phyll and some showing the peculiar spiral and ring-shaped thickenings on the 

 inner surface of the wall. 



5. Mount a piece of the main stem in water and examine under low power. 

 Draw, showing a central brown cylinder and a cortical layer of clear, large cells 

 with spiral thickenings. 



6. Cut off some of the clavate branches at the tip of the male plant, mount, 

 and sketch under low power. Pull off the scales carefully, mount, and examine 

 the antheridia. Draw an antheridium under high power, 



7. From a female plant carefully cut out an enlarged archegoniurn contain- 

 ing a young sporophyte. Mount and draw under low power, showing the neck 

 at the summit. Around the base some small archegonia may usually be seen. 

 Draw one of these, showing the stalk, venter, neck, and lid cells. 



Sporophyte. 



8. Pick out a young sporophyte showing the spherical capsule, the very 

 short stalk and the expanded bulbous foot. 



9. Cut off one of the slender pseudopodia containing a nearly mature sporo- 



