94 
Revicxv. 
thread-formation and branching which occur in Plcurococcus 
establish some case for taking it out of the Protococcalcs, but 
we can scarcely agree with a similar view of Gloeocyslis. The 
Coleochaetaceae are l ightly considered the highest segment of the 
Chaetophoraceous series. The name Chroolepidaceae is confined to 
the very natural little group of aerial forms— Treiitepohlia, Phyco- 
peltis and Cephaleuros (the Chroolepideae of the “ Revision.”) 
Professor Oltmanns divides the filamentous coenocytic pure 
green genera into two great groups : (1) Siphonocladiales including 
Cladophoraceae, (with Anadyoniene, Microdictyon and Dictyosphaeria), 
Siphonocladiaceae {Siphono clad us, Chamadoris and Struvea), Valo- 
niaceae {Valonia alone) and Dasycladaceae (with the usual genera), 
and (2) Siphonales. Though we entirely agree that the genera 
contained in the first three of these families should all be closely 
associated, the actual arrangement is unusual and seems insuf¬ 
ficiently justified in the text. The Dasycladaceae, though often 
technically “ siphonocladous ” certainly stand apart from the other 
group in virtue of their many peculiar characters. It is more probable 
that they are derived from some strictly siphoneous verticillate 
form in the neighbourhood of Dryopsis than from any of the true 
Siphonocladeae. 
The treatment of Siphonales calls for no special remark. 
We must pass very lightly over the great groups of the Brown 
and Red Seaweeds, though they actually occupy a little more than 
half the work. The Phacophyceae are divided into three primary 
divisions—the Phaeosporaceae, Akinetosporeae and Cyclosporeae. 
The Phacosporeae are again divided into four great families—the 
Ectocarpaceae, Cutleriaceae, Sphacelariaceac and Laminariaceae, and 
then again into sub-families. This arrangement permits a much 
readier general view of this difficult group than is the case when 
the non-cyclosporous Phaeophyceae are arranged in a great number 
of coordinated families. The Akinetosporeae are perhaps a 
somewhat provisional group, established to include the Tilopteridaceae 
and Choristocarpaceae with motionless spores. In the Cyclosporeae 
we have, of course, the two families, Dictyotaceae and Fucaceae. 
The discoveries of Lloyd Williams have certainly brought these 
two families so much nearer together that it is no longer advisable 
to place them in separate cohorts as Engler does. Williams’ most 
recent papers, however, with his striking discovery of a true 
alternation of generations in the Dictyotaceae, were, we suppose 
published too late to find a place in the present account. The 
description of the Fucaceae is excellent, but we could have wished 
