SECT. vi. SCALE MOSSES. 321 



genera, are merely fleshy fronds without veins, of nume- 

 rous and sometimes grotesque forms, while in the higher, 

 they are generally oval, and disposed in spiral imbricated 

 rows on each side of the stem and branches, every leaf 

 overlapping part of that which is adjacent to it like 

 a row of tiles. They are disposed after two distinctly 

 different plans. In one, the leaves are arranged in a 

 spiral, which turns from left to right ; consequently, the 

 anterior border of each inferior leaf is covered by the 

 posterior border of that immediately above it. This 

 constitutes the succubous group of frondose Junger- 

 mannieae, which embraces five tribes. In the second 

 case, the spiral of the leaves turns from right to left, 

 and the anterior border of each inferior leaf covers the 

 posterior border of that immediately above it. This 

 constitutes the incubous group embracing three tribes 

 of the frondose Jungermanniese. Besides the imbricated 

 spiral leaves, there are small leaves alternating with 

 them, and applied directly on the stem between them. 



The male fruit of the Scale Mosses consists of 

 antheridia, which form ovoid masses of cells variously 

 disposed; in each of these cells, there is a filiform 

 spermatozoid coiled in a circle in active motion, which 

 is maintained after leaving the cell. The female fruit 

 consists of archegonia, containing embryo cells, which 

 ultimately develope into sporangia ; but the plants arrive 

 at their full development before the archegonia appear. 

 The same plant may produce more than one crop of 

 these objects, which are occasionally abortive. The stalk 

 of the sporangium is first surrounded by the sac of the 

 archegonium, then by an involucre or circle of bracts, 

 placed in a rosette of leaves. The sporangia contain 

 cells which ultimately become spores mixed with long 

 cells containing elaters, that is, elastic spiral filaments. 

 When the fruit is ripe, the sporangia split into four 

 equal parts, which form a cross on the top of their 



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