VEGE TA TI I 'E KEF ROD UCTION. 



26l 



from spores until the mossworts are reached, in which the 

 alternation of phase is well marked. In their simplest form 

 such buds consist of a single cell, though more commonly 

 they are two- to several-celled. Some or all of their cells are 

 in the embryonic stage (^f 256). Like spores, they are sup- 

 plied with reserve food. 



362. Simple forms.- -The form of brood buds is various. 

 When not differentiated into distinct organs, they are club- 

 shaped, lenticular, or spherical. In some thalloid liverworts 

 (Marchantia and Lunularia) they are produced on the surface 

 of the thallus, surrounded wholly or on one side by an out- 

 growth from the surface forming a cup or a crescentic ledge 

 (figs. 59, 290, 291). In some mosses brood buds arise from 



FIG. 290. Thallus of Marchantia, seen from above, showing the cups containing brood 

 buds. See fig. 291. Natural size. After Kerner. 



the apex of the stem, either in cup-like clusters of leaves or 

 exposed (A, A' ', fig. 292) ; in others they are smaller and 

 simpler and are developed upon the leaves (J3, B' , fig. 292). 

 In all the mossworts they belong to the gametophyte. 



363. Shoots. --In fern worts and seed plants the brood buds 

 belong to the sporophyte. In the latter they are especially 

 abundant, and often reach considerable size and complexity 

 before being separated from the parent, usually consisting of 

 a short axis with a growing point and at least rudimentary 



