II MUSCINE^—HEPA TIC^— MARCH ANTI ALES 19 



most Jungermanniales the wall of the capsule splits vertically 

 into four valves. 



The spores are always of the tetrahedral type, i.e., the 

 nucleus of the spore mother cell divides twice before there is 

 any division of the cytoplasm, although this division may be 

 indicated by ridges projecting into the cell cavity, and partially 

 dividing it before any nuclear division takes place. The four 

 nuclei are arranged at equal distances from each other near the 

 periphery of the mother cell, and then between them are formed 

 simultaneously cell w^alls dividing the globular mother cell into 

 four equal cells having a nearly tetrahedral form. These 

 tetrads of spores remain together until nearly full grown, or in 

 a few cases until they are quite ripe. In the ripe spore two, 

 sometimes three, distinct coats can be seen, the inner one 

 (endospore, intine) of unchanged cellulose, the outer one 

 (exospore, exine), strongly cutinized and usually having upon 

 the outside characteristic thickenings, ridges, folds, spines, etc. 

 Where these thickenings are formed from the outside they 

 constitute the third coat (perinium, epispore). The exospore 

 is especially well developed in spe'cies wdiere the spores are 

 exposed to great heat or dryness, and w^hich do not germinate 

 at once. In those species that are found in cooler and moister 

 situations, especially where the spores germinate at once, the 

 exospore is frequently thin. The nucleus of the ripe spore is 

 usually small. The cytoplasm is filled with granules, mostly 

 albuminous in nature, with some starch and generally a great 

 deal of fatty oil that renders the contents of the fresh spore 

 very turbid. Some forms, especially the foliose Junger- 

 manniaceae, have also numerous chloroplasts, but these are lack- 

 ing usually in those forms that require a period of rest before 

 germination. In Pellia and Conocephalus the first divisions in 

 the germinating spore take place while the spores are still 

 within the sporogonium. 



The germination of the spores begins usually by the forma- 

 tion of a long tube (germ-tube, "Keimschlauch" of German 

 authors), into which pass the granular contents of the spore. 

 At the same time there may be formed a rhizoid growing in 

 a direction opposite to that of the germinal tube, although quite 

 as often the formation of the first rhizoid does not take place 

 until a later period. If the spore does not contain chlorophyll 

 before germination, it is developed at an early stage, before any 



