484 Fritsch . — The Structure and Development of 
membrane of the zoospore itself sometimes presented such 
thickenings (Fig, 25,/), and the difference in colour between 
the two kinds of mucilage on the addition of Iodine is then 
readily perceived. 
5. Summary. 
The more important results obtained in the present paper 
may be briefly summarized as follows : — 
1. Certain types of root-ends are characteristic for certain 
species of Oedogonmm ; thus the attaching-disc and rhizoid for 
Oed. calcareum , capillare , and stagnate , the rhizoid alone for the 
species from the river Severn, and the attaching-disc and sack- 
shaped basal end for Oed. cardiacum. 
2. The brown substance, which is so frequently found in 
connexion with the young plants of Oedogonium , consists of 
ferric oxide or of some salt thereof. 
3. The casting-off of the first cap is by no means the rule 
in this genus, although occurring fairly constantly in some 
species (e. g. Oed. cardiacum). 
4. The colourless state, into which the filaments of this 
Alga sometimes pass over, is probably a gradual dying-off of 
the plant. 
It remains for me to express my sincere thanks to my 
friend, Mr. L. A. Boodle, F.L.S., for several valuable sugges- 
tions made in the course of this work. 
