88 BOTANICAL GAZETTE [january 



Rot of potato tubers. — Hawkins, 14 continuing his studies on the effect of 

 various fungi on their hosts, has investigated the effect of Fusarium oxysporum, 

 F. radicicola y and F. coeruleum on the sugar content, both sucrose and reducing 

 sugar, pentosans, methyl pentosans, galactans, dry matter, starch, and crude 

 fiber of the potato tuber. The crude fiber content of the tubers was not reduced, 



m 



starch and methyl pentosans were not affected appreciably, while the content 

 of the other substances was reduced. It is interesting from the point of view 

 of resistance to fungus invasion that the least digestible forms occur in greatest 

 proportions in the skin and cortical regions of the tuber. Fusarium oxysporutn 

 and F. radicicola were found to secrete sucrase, maltase, xylanase, and diastase. 

 The diastase, like the malt diastase that Brown and Morris worked with, is 

 incapable of attacking ungelatinized potato starch. — George K. K. Link. 



Phytoplankton of the oriental tropics. — Ostenfeld 1 * has published a list 

 of the phytoplankton of one of the straits of the Malay Archipelago. The 

 list is based chiefly upon a large collection of drawings made by P. Th. Juste- 

 sen in 1909 and 1910, while residing at one of the small military stations in the 

 Dutch Indies. The list includes 100 species, the largest group being the 

 diatoms, with 56 species representing 23 genera. The Peridiniales constitute 

 the other large group, including 40 species in 11 genera, the largest genera 

 being Ceratium with 17 species, and Peridinium with 12 species. The general 

 character of the plankton is said to be that of a "tropical neritic plankton/' 

 very much like the plankton examined by Cleve and Ostenfeld from the 

 Malay Archipelago and the Gulf of Siam. — J. M. C. 



Branched prothallia. — Miss Wuisx 16 has investigated the early stages of the 

 gametophytes of the Polypodiaceae in reference to branching, subjecting them 

 to various culture conditions. She observed branching in cultures of 15 species 

 representing 9 genera. Branching, which was both dichotomous and mono- 

 podial, was not a response to any one type of culture medium, but appeared 

 on distilled water, on soil, and on various nutrient solutions. Branches did 

 not appear at any definite period in the life history of the gametophyte, but 

 were formed by any cell of the filament, by divisions of the last cell of the fila- 

 ment, and from the margin and apex of the expanded portion of the pro thallium. 

 The author has concluded that a definite relation exists between branching 

 and nutrition. — J. M. C. 



14 Hawkins, Lon A., Effect of certain species of Fusarium on the composition 

 of the potato tuber. Jour. Agric. Research 6:184-196. 1916. 



^Ostenfeld, C. H., A list of phytoplankton from the Boeten Strait, Celebes. 

 Dansk Bot. Arkiv 2:no. 4. pp. 18. figs. 10. 1915. 



x6 Wuist, Elizabeth D., Branched prothallia in the Polypodiaceae. Bull. Torr. 

 Bot. Club 43:365-383- figs. 15. 1916. 



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