THE MICROSCOPE IN HISTOLOGY AND BOTANY. 151 



97. Encyonema. Frond filamentous, but little branched ; 

 fr. like Cymbella ; aquatic. 



98. Syncydia. Fr. those of Gymbella, united in circular 

 bands, immersed in an amorphous gelatinous frond ; ma- 

 rine. 



99. Frustulia. Fr. as Navicula, irregularly scattered 

 through an amorphous gelatinous mass ; aquatic. 



100. Micromega. Fr. as Navicula, arranged in rows in 

 gelatinous tubes, or surrounded by fibres, these being in- 

 closed in a filiform branched frond ; marine. 



The family of Nostochince is allied to the PalmellacecK. 

 It consists of beaded filaments suspended in a gelatinous 

 frond. The gelatinous masses of Nostoc often appear quite 

 suddenly in damp places, and have been called "fallen 

 stars." They attracted the notice of the alchemists, and 

 enter into many of their recipes for the transmutation of 

 metals. What have been termed showers of flesh or of 

 blood, originated in all probability in the rapid develop- 

 ment of similar masses. Many botanists regard them as 

 the " gonidia " of Collema and other lichens. 



The Oscillatoria, so called from the singular oscillatory 

 motion of their filaments, consist also of cells which mul- 

 tiply in a longitudinal direction by self-division. The 

 Ulvacece, to which the grass-green sea-weeds belong, in- 

 crease in breadth as well as length by the subdivision of 

 cells, so as to produce a leaf-like expansion (Plate X, Fig. 

 112). An illustration of the simpler forms of reproduction 

 in Protophytes is seen in Zygnema, so called from the sin- 

 gular manner in which the filaments are yoked together 

 in pairs. In an early stage of growth, while multiplica- 

 tion of cells proceeds by subdivision, the endochrome is 

 generally diffused, but about the time of conjugation it 

 arranges itself usually into a spiral. Adjacent cells put 

 forth protuberances, which unite and form a free passage 

 between them, and the endochrome of one cell passes over 



