THE SPORANGIA OF HALIMEDA 195 
grow out in small isolated tufts . these angles, in the place where 
new joints might otherwise be fig 
According to the system of classification of species described 
Bi the distinguishing feature of H. gracilis lies 1 in the complete 
fusion of the filaments of the central strand in pairs at the apex of 
a joint; the fused portion is prolonged, and then branches tricho- 
tomously in the next joint. When the — —_— is aaa 
g 
sporangia are empty, but t has been possible to find specimens in 
which th ripe sa ai still ‘alls the sporangia and the apex of the 
sporangiophore. The protoplasm is studded with small black dots, 
and the condition is probably one shortly preceding the escape of 
the zoospores. 
Sporangia of H, Tuna. 
In H. Tuna the filaments of a joint do — as in A. gracilis, 
form three conspicuous ribs; but, on the contrary, numerous 
cea strand-filaments ‘radiate flabellately peti the base of a 
joint, and run out to the margin, where in a purely vegetative joint 
they | remain without further developm ent. (Besides these radiating 
filaments there is of course a main strand, which is rather in- 
distinct, forming the axis of the joint, and continuing its course 
into and through the joint above.) In a fertile joint these ere 
margin, and em erge to bear sporangia. Thus in H. Tuna the 
of communication between the fusing ecenoreh of the 
central strand of H. Tuna takes place in the manner described 
above on p. 194. Two, sometimes three, filaments fusing together 
form a single filament, but, whereas in the case of the main strand, 
which has a igs vegetative function, the single filaanant resulting 
from the fusion continues its course into the next joint badors 
& 
OQ 
two long branches. These branch dichotomously at the top, and 
each wr branch bears sporangia similar in forma to those of 
» graci 
The pileumnes between the fruits of H. gracilis and H. Tuna 
may therefore be summarized as follows:—In H. gracilis the 
smorene vances arise in ‘soled tufts an the angles of a joint; 
- Tuna they form a continuous fringe alon the margin of a 
nes In H. gracilis the filament resulting from the fusion of two 
saat: of the central strand grows out as a single long filament 
o 2 
