1924] Lewis,—The Flora of Penikese 191 
However, 14 species, now so abundant both at Penikese and in the 
surrounding waters as to be fairly considered as representative species 
of the present flora and by no means likely to be overlooked, were 
missing in 1873. These are: 
Anabaena torulosa Punctaria latifolia 
Chaetomorpha Linum : Ralfsia verrucosa 
Enteromorpha Linza Seytosiphon lomentarius 
Chorda filum Chondria Baileyana 
Desmarestia aculeata Nemalion multifidum 
Ectocarpus confervoides Phyllophora membranifolia 
Ectocarpus fasciculatus Polysiphonia fibrillosa 
On the other hand, Jordan lists some species which are now abundant 
in the general region, the absence of which at Penikese is surprising, 
though it is perhaps to be explained by the short time devoted to the 
survey. Such species as those included in the following list are 
certainly to be expected at Penikese, even though the rich list of 
Callithamnions and of the more delicate Polysiphonias given by 
Jordan is not likely to be duplicated at the present time. 
Cladophora gracilis Callithamnion Baileyi 
Enteromorpha clathrata Dasya elegans 
Sargassum filipendula Griffithsia globifera 
Antithamnion americanum Polysiphonia variegata 
DIATOMS.! 
The island of Penikese has been inaccessible until recently because 
of its use as a State leper colony, and this, together with its somewhat 
isolated location, lends rather more than usual interest to the flora 
found there. Its small size, isolated location, and the nature of its 
topography form a rather severe set of factors in limiting the diatom 
species found in this flora. The island has a number of small ponds, 
and those which are not low enough to be subject to occasional in- 
vasions by the waves and tides of the sea are replenished only by the 
frequent rains which fall in that region, and hence are subject to 
occasional drying-up in periods of extended drought. From the 
former are excluded such diatoms as are not brackish in habitat or 
else not hardy enough to stand changes in the salinity of the water. 
Occasional drying-up of the other ponds may be somewhat of a factor 
in their diatom life, although the humidity of the atmosphere and the 
brevity of such dry periods probably allows the diatom life to go on 
1! By Paul S. Conger, Carnegie Institution of Washington. 
