12 Transactions of the Society, 



instances of growth with which I am acquainted. In one example, 

 when first observed (fig. 22) the new pieces were but shghtly 

 smaller than the old pieces, only partially filled with endochrome, 

 and the cell-wall perfectly smooth. While under observation and 

 drawing they grew to their full size, and became entirely filled 

 with endochrome. The first appearance of spines was now seen ; 

 they rapidly increased in stoutness, and within an hour from the 

 time of first observation the new individuals were perfectly formed. 

 During the whole of this time the individual was in constant 

 motion, but became quiescent as soon as the new formation was 

 completed. The pair remained in contact till the next morning. 



Staurastrum Pringsheimii Eeinsch. 

 alternans Breb. 

 punctulatum Breb. 

 dilatatum Ehrb. 

 polymorphum Breb. 

 gracile Ealfs. 



levispinum Biss. (Joum. E. Micr. Soc., 1884, 

 p. 195, t. V. fig. 5). 

 „ controversum Breb. 



Staurastrum tuberculatum n. sp. Fig. 24. 

 Frond moderately large, 70 fi long by 55 fi broad ; each frustule 

 nearly hexagonal in shape, 37 fi broad at the apex, 30 /j, at the 

 isthmus ; the terminal and upper lateral edges nearly straight or 

 slightly convex ; the lower lateral edges concave. The whole margin, 

 except the lower lateral edges, rough with pearly granules, which 

 are larger at the corners. Surface of frond tuberculated. 



Bog pool, Loughrigg. Belongs to the 'section with concave 

 sides ; near to S. nitidum Arch, and iS". Sehaldi Eeinsch. 



Staurastrum ? enorme Ealfs. Fig. 25. 



This rare and remarkable desmid was gathered in a bog pool on 

 Park Fell. Although, as described by Ealfs, it is by far the least 

 symmetrical species of the genus, the bilateral symmetry is never- 

 theless seen in certain positions. The frustules are tuberculated, 

 and from each tubercle springs a cluster of hyaline spines with a 

 common base. Some writers give this as a synonym of Polyedrium 

 enorme dBy., but probably in error, as a figure in Cooke's ' British 

 Fresh- water Algas ' certainly does not represent this plant. 



Arthrodesmus convergens Ehrb. 



„ Incus Breb. 



Cylindrocystis diplospora Lund. (Desm. Suec, p. 83, t. v. 

 fig. 7.) 



Frequent. Probably frequently overlooked from its resemblance 

 to the bicellular condition of a Mesocarpus, but easily distinguished 



