SPORES AND THALLIDIA. 



23 



which has not been in any way a result of fertiHzation. These aggregates of cells 

 are, in a manner, structures intermediate between the unicellular spores and the 

 buds, differentiated into axis and leaves, which occur in vascular plants. They 

 are portions of the thallus which produced them, and are either very like it or 

 assume the same form as soon as their further development is complete. Hence 

 the most appropriate name for these bodies is that of thallidia (ea\\6s = young 

 shoot; er5os = a likeness). They are also known as gemmce. Thallidia are some- 



Pig. 196.— Thallidia of Muscineae. 



L Slarcnantia polymorpha with cups containing thallidia or gemmse. 2 Longitudinal section of thallidial or gemmiferous cup. 

 8 A single thallidium. * Tetraphis pellucida. 5 x stem of Tetraphis bearing a cup containing thallidia. 6 Longitudinal 

 section of a thallidial cUp. ^ 8 Isolated thallidia of Tetraphis. 9 A stem of Leucodon saiuroides with brood-bodies. 10 a 

 brood-body set free from the stem. " Development of a brood-body from the rhizoids of a leaflet torn from Cavfipylopus 

 fragilis. ^, ^% 1* Development of thallidia at the apex of a leaf of Syrrhopodtm scdber. is Aulacomnion androgynum-. 

 16 A stem of the same bearing thallidia. i', is Single isolated thallidia. 1 natural size ; *, is x 2 ; 2, 12, is x from 8 to 16 ; 

 6_ 6^ 9^ io_ 14 X from 20 to 40; », ', ', ", 18x120. 



times in the form of rows of cells, as, for example, those developed on the leaflets 

 of the Moss Syrrhopodon scaber (see figs. 196 ^^■^^' ^*); sometimes they are nets, as in 

 the Water-Net (Hydrodictyon, see figs. 197 1- *■ ^). In the Moss Tetraphis pellucida 

 (see figs. 196*'^'^''''*) they occur as plates of cells, and in other cases they assume the 

 form of globular or ellipsoidal lumps of tissue, as, for instance, in the Moss Aulacom- 

 nion androgynum (see fig. I96i6, i6,i7,i8^_ Sometimes the number of cells associated 



