ANTHOCEROS 125 



3. Spores and elaters frequently held within the split spore case. Draw 

 a sporophyte and details of the spores and elaters. 



4. Lengthwise microtome sections of archegonial branches (Sec. 212) 

 give extremely interesting slides of various stages in the development 

 of the sporophytes, showing the foot and details of the spore case 

 when the latter is still contained within the archegonium (see Prin- 

 ciples, Fig. 256). Note the f our-lobed spore mother cells, or the groups 

 of four spores, tetrads, produced by them. Compare this sporophyte 

 with that of Marchantia. Draw its characteristic features in detail. 



Reference. Campbell, 23. 



126. Anthoceros, the horned liverwort. This type is chiefly interesting for 

 the sporophyte. 



A. The sexual plants, or gametophytes. Note the relatively small thallus, 

 lobed but unbranched and with an irregular margin. Contrast its sim- 

 plicity with the gametophytes of Marchantia and Porella. Make a 

 habit sketch to show these points, together with the elongated sporo- 

 phytes which rise from the thallus. 



1. The vegetative structure may be studied from cross sections cut in 

 pith. Observe the simple cell structure, each cell containing a, 

 single large chromatophore. Note the cavities on the lower side gen- 

 erally containing colonies of the blue-green alga, Nostoc. 



2. The sexual organs are best examined from microtome sections and 

 form a detailed study. 



B. The sporophyte. Observe the sporophytes of various ages developing 

 upon the gametophyte, rising out of cylindrical collar-like outgrowths 

 of the gametophytes. 



1. Study and draw the oldest sporophytes, noting how they split into 

 two parts, which separate, and the delicate thread of shriveled 

 sterile tissue (columella) which rises between. Pick such a sporo- 

 phyte off and mount entire. Where are the ripe spores formed ? 

 Examine the surface for pores, or stomata, with guard cells. 



2. Lengthwise microtome sections of the sporophytes (Sec. 212) in- 

 cluding portions of the thallus will show the remarkable foot, region 

 of growth, and the cylinder of spore-producing tissue (archesporium), 

 with stages in the development of the spores and other details of 

 cell structure of great interest (see Principles, Fig. 258). 



This sporophyte is the most interesting of any in the liverworts because 

 of a number of features suggestive of life habits in higher plants. Chief 

 among these are the stomata, the long period of growth and fructification, 

 and the large foot drawing water from the gametophyte. 



Reference. Campbell, 23. 



