MOSSES. 



[ 432 ] 



MOSSES. 



forms of which are used as characters by 

 systematic Muscologists. They are either 



466. 



all alike in a leaf, and filled 

 with chlorophyll, and in these 

 cases may be either paren- 

 chymatous (PL 38. fig. 19) or 

 prosenchymatous (PI. 38. fig. 

 20), or several rows running 

 up the centre are more elon- 

 gated than the rest, and give 

 the appearance of a mid-nerve. 

 In other cases two sorts of 

 cells occur arranged in a pe- 

 culiar way ; some, smaller, 

 containing chlorophyll, form a 

 kind of network, the meshes 

 of which are occupied by large 

 uncoloured cells (see SPHAG- 

 NUM and LEUCOBRYUM). 



The leaves often differ on 

 different parts of the stem, 

 and we hence have radical, Ma S n - 50 diams> 

 cauline, and perichcetial or involucral leaves, 

 the last ordinarily forming a kind of rosette, 

 in the midst of which the reproductive or- 

 gans are produced. SCHISTOSTEGA exhibits 

 two forms of stem, with two kinds of folia- 

 ceous structure ; the stems which terminate 

 in a sporange have leaves only at the upper 

 part, and these arranged in eight rows stand- 

 ing crosswise on the stem, like ordinary 

 leaves ; the barren stems have two rows of 

 leaflets arranged in one plane on the stem, 

 like the leaflets of a compound leaf (such as 

 that of the Acacias) of Flowering plants. 

 The stem-leaves of many genera exhibit 



Fig. 467. Fig. 468. 



Leaf. 



Barbula chloronotus. 

 Fig. 467. Leaf with cellular filaments at the tip. Magn. 



30 diams. 

 Fig. 468. Leaf with cellular filaments crowded on the 



midrib, with an arm-like prolongation. 



Magn. 20 diams. 



wing-like structures, hair-like appendages, 

 or peculiar forms of curvature (figs. 255-50, 

 FISSIDENS); others, like certain Barbulce 

 (figs. 467-470), have collections of cellu- 

 lar filaments on the upper side. 



Fig. 469. 



Fig. 470. 



Barbula chloronotus. 



Fig. 469. Cross-section of 467. Magn. 50 diams. 

 Fig. 470. Cross-section of 468. Magn. 50 diams. 



The outer leaves surrounding the repro- 

 ductive organs are called perichcetial, and 

 sometimes they form the only envelopes; 

 sometimes, however, a few small leaves, dif- 

 fering very much from the above, form the 

 immediate envelopes of the archegones, and 

 these perigonial leaves, forming the peri- 

 gone, are developed afterthe reproductive or- 

 gans themselves (as is the case also with the 

 perigone of the Hepaticacere). The perigo- 

 nial leaves either overlap and cover in the 

 reproductive organs, or they are keeled at 

 the base and turned back above, so as to 

 expose the organs of reproduction (POLY- 

 TRICHUM). 



The young reproductive organs consist of 

 antheridia and archegonia or pistillidia, which 

 are found either together (fig. 471) in the 



Fig. 471. 



Fig. 472. 



Bryum nutans. 



Fig. 471. Inflorescence of antheridia and archegonia. 



Magn. 25 diams. 

 Fig. 472. Spermatozoids from antheridia. Magn. 600 



diams. (The cilia omitted.) 



same perigone, or on different parts, or on 

 different individuals of the same species. To 

 these structures the term inflorescence is 

 applied. The antherids occur either with 

 the archegones in one perigone (fig. 471) or 

 in the axils of the upper leaves of the stem, 

 which terminates in a perigone containing 

 archegones ; or they have a special perigone 



