Noteworthy anatomical and physiological researches. 
The rhizoids of filamentous algz.' 
While a few theories have been advanced to explain the 
occasional formation of rhizoids on those forms of filamentous 
Chlorophyceze on which rhizoids do not normally occur, the 
author is the first to attempt to demonstrate their cause by 
experiment. 
The observations were made from artificial cultures of two 
kinds, the so-called ‘‘contact cultures” and suspended cultures. 
In the former, the cultures were made either on a slide, be- 
tween a slide and a cover glass, or in a hanging drop. In the 
suspended cultures a tuft of alge is tied about the center with 
a slender linen thread, all rhizoids having first been removed, 
and suspended in a culture fluid. By this means liability of 
one filament coming in contact with another is in most cases 
removed. Various substances were used in making the media, 
and these in different degrees of concentration. The author 
gives in detail cultures made in solutions of agar-agar, gum, 
albumen, urea, cane sugar, milk sugar, erythrite, asparagine, 
glucose, dulcite, mannite and glycerine, and mentions cul- 
tures made in solutions of citric acid, berberine, potassium tar- 
trate, sodium chloride, potassium nitrate, potassium sulphate, 
Magnesium sulphate, sodium nitrate, aluminum sulphate, potas- 
sium alum, and in stained solutions of indigo carmine and 
nigrosin. None of the latter, however, were very success~ 
ful, as the staining prevented the free action of light, and in 
the others the alge died, even in very weak solutions. 
The first results were obtained in contact and water sus- 
concludes that rhizoid formations of Spirogyra depend upon 
certain external influences from contact with a firm body. 
Notwithstanding the great number of cultures made, he con- 
fesses that his investigations are insufficient to fully explain 
the nature of these external influences. 
__ ‘it the two extremes of the series are the contact cultures 
*Borce, O. Ueber die Rhizoidenbildung bei einigen fadenformigen Chlorophy- 
ceen, Upsala, 1894. 
[417] 
