206 NOTES ON THE FLORA OF MALTA. 
tinous mass." The indefiniteness of this description is not removed by 
the illustrative figures of the forms. Subsequently the last-named author 
amended the genus and thus described it, ** Frustula navicularia solitaria 
vel geminatim— conjuncta, libera vel in muco amorpho nidulantia, valvis 
elliptico-lanceolatis nodulo centrali terminalibusque destitutis linea 
media medio interrupta." (Flora Europ. Alg. sect. 1, p. 227.) It 
is doubtful whether the character expressed in these words, “ nodulo 
centrali terminalibusque destitutis," really applies to the forms Ra- 
benhorst embraces in the genus; but if it be correct, it can seareely 
agree with Pfitzer's description of the genus Frustulia as adopted by him, 
the characters of which are the strong longitudinal lines placed on either 
side of the median line, and the very peculiar form of the modules. 
arrangement of the internal contents of the cell is in the main the same as 
in that of the Navicule, but distinguished by this peculiarity, that the en- 
doehrome plates on either side in the middle of the cell are pushed out 
from the cell-walls by the interposition of a half-spherical mass of plasm. 
- The division of the endochrome plates in the case of N. sazonica occurs by 
fission from the ends throughout, without any movement of the plates 
within the cell. - 
servable here, as are also the two masses of plasma interposed in the 
middle, between the cell-wall and the endochrome plates. Division of the 
€ 
stances of the movement and division of the endochrome plates were J 
as in Navicula. 
In Colletonema subcoherens, according to the observation of Thwaites, 
two mother-cells produce two auxospores, and the process occurs occasion- 
mith, one mother-cell produces one auxospore, but according to f 
this is abnormal, and occurs only when one of the auxospores withers 0%, 
the general rule being that two cells co-operate to produce two auxospores, 
NOTES ON THE FLORA OF MALTA AND GOZO. 
By J. F. Durnin, B.A. 
A residence of five months in Malta during the past winter and à 
portion of the spring has enabled me to gain some information concerning: 
