196 Rhodora [OCTOBER 
AN ALGOLOGICAL PROPHECY FULFILLED. 
F. S. COLLINS. 
I mave lately taken considerable interest in those forms of algae that 
show special adaptations to particular conditions, epi- or endophytic, 
epi- or endozoic habitat, and the like, of which many are known, both 
fresh water and marine, and doubtless many more will be discovered. 
One for which I have been looking is Dermatophyton radians Peter, 
a green alga that forms a firm crust on the backs of turtles, penetrating 
into the crevices; it was first found in Europe, and has once been 
found in this country. For the last two or three years I have waylaid 
turtles at many ponds, but have found no trace of the alga; the shells 
have been bare and smooth. But one day in June last, in Tewksbury, 
Massachusetts, I saw a turtle near the edge of a pond, with a distinct 
green growth on the shell. I proceeded towards him with the utmost 
caution, as turtles are not easily taken unaware, but soon a sense, other 
than sight, notified me that he was not likely to escape; he was no ways 
superior in appearance to other mud turtles, and yet it would hardly 
be incorrect to speak of him as unapproachable. I succeeded in 
scraping off some of the growth, which as I had supposed was a green 
alga, but it certainly was not the Dermatophyton; the substance was 
much softer. Only when I reached home and examined it with the: 
microscope did I recognize it; it was Chaetomorpha Chelonum, the 
plant that I described in Кнорока, Vol. IX, p. 199, from material sent 
me from Michigan, where Dr. Hankinson found it on two species of 
turtle. Now in connection with my description I referred to what 
Lagerheim said, when describing C. herbipolensis, the first, and until 
my note the only certain fresh water species of this genus; that the 
desmids that he had studied on specimens of aquatic phanerogams, 
collected long ago by B. D. Greene, indicated that the algal flora of 
Massachusetts was of almost a tropical character, and that fresh 
water species of Chaetomorpha were to be expected here. "The char- 
acterization of Massachusetts as subtropical strikes one rather oddly, 
but here is this second station for C. Chelonum, the same Round Pond 
where Greene collected the plants that Lagerheim examined in the 
herbarium in Sweden, and from which he published his very valuable 
list of desmids; I had been exploring many ponds all over New Eng- 
