366 
Notes . 
cells are formed (Figs. 6, 7). In the mature stage the original boundary lines of an 
epidermal cell will be very sinuous, while those division lines which are formed within 
an epidermal cell will take a much less sinuous appearance (Figs. 5, 8-10). 
Occasionally in the above described three-celled stage, one of the marginal 
cells, instead of the central one, becomes a stoma-mother-cell. In this case, an 
Fig. 8. A mature stoma with divided subsidiary cells. 
x 450 - 
Fig. 10. 
Figs. 9, 10. ‘ Twin stomata ’ ; Fig. 9 being not quite typical, x 450. 
epidermal cell or a division of an epidermal cell abutting on the stoma would take the 
place of a subsidiary cell. It often happens, in such a case, that the other part of the 
epidermal cell further divides once or twice and forms another stoma, so that a ‘ twin- 
stoma ' results (Figs. 9, 10). Except in rare cases, it has been observed that a perfect 
6 twin-stoma ’ is not formed from one single epidermal cell, but usually one of the 
neighbouring epidermal cells will join as a subsidiary cell (Figs. 9, 10). 
Very seldom a stoma is formed diagonally to the epidermal cell, as has also 
been observed in the cotyledon and bract of Welwitschia. 
H. TAKEDA. 
The Royal College of Science, 
London. 
NOTE ON AN ATTACHED SPECIES OF SPIROGYRA.— It is well known 
that members of the Zygnemaceae do not, as a rule, form attaching organs, 
the filaments being commonly found floating freely in still or slowly running fresh 
water. There are, however, species of Spirogyra on record which are frequently 
attached to some substratum : such are S. adnata and -S’, fluviatilis , which are often 
found anchored to submerged stones, and S. setiformis , which according to Kny may 
occasionally be attached by rhizoids, but is more often found in freely floating masses. 
Rhizoids have also been observed in other species of Spirogyra , and in species of 
Zygnema and Mougeoiia, but only under special conditions, either in culture solution, 
or during conjugation as irregular outgrowths from a conjugating tube. We have 
