MARCHANTIA 119 



1. That the sporopliyte is contained witliin a celhilar envelope, calyptra. 

 Observe the positions of IJie sporophytes witli relation to the midrib 

 region of the thallus. 



2. That tlie sporophyte has a delicate wall composed of a layer of cells 

 within the calyptra, and contains developing or mature spores. 



3. That the spores are formed in groups of four, tetrads, within spore 

 mother cells. 



4. The markings on the walls of mature spores. 



5. In median sections the shriveled remains of the neck of the arcJie- 

 gonlum, whose very much enlarged base is now the calyptra. 



Illustrate as many of these points as possible in a semidiagrammatic 

 drawing. 

 D. The structure of the sexual organs and development of the sporophyte. 



These are best studied from lengthwise sections cut in paraffin with 



the microtome and stained. 

 Reference. Campbell, 23. 



124. Marchantia. It is well to examine first, in comparison 

 with one another, male and female plants and those devoted 

 chiefly or exclusively to bud formation. In living material study 

 the growth habits in relation to earth, dampness, and light. 



A. General morphology. Note : 



1. The upper and lower surfaces. How are they distin- 

 guished ? 



2. The ribbon-like form of the thallus, the method of branch- 

 ing. Is it a mode of forking, and why are the branches 

 irregular in length ? 



3. The notched tips of the branches where the cji^oicing points 

 are situated. Find a specimen whose tip has recently 

 branched so that there are two growing points close 

 together but diverging. 



4. A central line, or midrib, running into each branch, forking 

 when the thallus forks, and ending in the growing points. 



5. The character of membranous /rmp'es and filaments, rJti- 

 zoids, on the lower surface, and their distribution with 

 especial reference to the midrib region. 



6. The presence of stalked disks or nmbrella-Uke structures, 

 which bear the sexual organs, or of cups, containing Imds. 



Illustrate as many of these points as possible in sketches. 



