198 -Rhodora [OcrosER 
P. miniatus (Protococcus miniatus Kütz., Pleurococcus miniatus Nüg.), 
which is not uncommon on walls and windows of greenhouses, but 
whose native habitat is unknown; Chodat reports its reproduction 
under ordinary circumstances to be by bipartition, rarely quadri- 
partition of the cell; but in culture in pure spring water the contents 
of a cell is by repeated division sometimes transformed into 16, 32 or 
64 spores with delicate membrane, escaping in a mass with a gelatinous 
envelop. This latter form of reproduction is the only one observed 
in P. marinus, but practically all of the Harpswell material seemed to 
be in some stage of this process. The color of the cell ranges from 
deep orange to pure green; the largest cells were green, but cells of 
this color were found of all sizes down to the smallest. The only dis- 
tinction other than color was that the largest green cells had a thinner 
wall than the small or moderate sized cells, either green or orange, and 
that the colored cells seemed more active in spore formation. The 
wall of the spore was fully developed while the wall of the mother cell 
was still perfect; after the disappearance of the latter the spores 
remained in a spherical gelatinous mass for a long time, until they 
had increased very materially in size; colonies of 32 cells were observed, 
retaining the spherical form with a diameter of 100 u. Some of the 
plant was kept alive for several weeks, but not under the normal 
conditions of a salt marsh pool; in this material were finally found 
numerous spherical colonies, in which the contents of each cell had 
divided into aplanospores of a second generation, much smaller than 
any noticed in the normal condition of the plant. From P. miniatus, 
P. marinus is distinguished by the larger cells, those of P. miniatus 
being 3-15 p diam.; by the thicker walls of the aplanospores, and 
by the totally different habitat. According to the figures of P. 
miniatus in Chodat's Algues Vertes de la Suisse, fig. 80, the gelati- 
nous vesicle of the spores is less regular in form in that species and 
less persistent. , 
Chaetomorpha Chelonum n. sp. Filamento erecto, stricto, 12- 
20 y» diam. ad basin, superne incrassato, usque ad 35 y in fronde sterili; 
cellula basali ad 1 mm. longa, cellula proxima ad 10 diam., cellulis 
superioribus 2-3 diam. longis; membrana cellulari crassa; cellulis 
fertilibus in parte superiori filamenti ortis, ad 50 & diam., 1—4 diam. 
longis, leviter aut admodum moniliformibus aut enim subglobosis; 
zoosporis per aperturam in media parte cellulae ct tubum tenuissimum 
exeuntibus; ramis pluricellularibus, coralloideis, e cellula basali 
exeuntibus, stratum basale continuum substrato arctissime ad- 
haerentem formantibus. 
