1908] CURRENT LITERATURE 149 
there is a distinct factor present for the mosaic condition, so that the sex of such 
plants is not to be looked upon as due to the presence of the male- and female- 
producing units alone, but to the presence of a factor determining the tendency 
to be hermaphrodite or monoecious respectively. 
The field for investigation which has thus been thrown open is a very inviting 
one, and it is to be hoped that other dioecious species which have nearly related 
hermaphrodite or monoecious species among both plants and animals will be 
made to yield whatever support they may for the generalizations CorRrENS has 
made.—GrorceE H. SHULL. 
Plankton of Illinois River 
Four years ago, this journal reviewed the first part (1903) of Korom’s 
Plankton of the Illinois River, which dealt with the quantitative investigations and 
general results. There has just appeared the second part, which deals with 
the organisms of the plankton and their seasonal distribution. The character 
of the work, with its mass of statistics, forbids an adequate review. As was stated 
in the preceding review, this series forms the most important contribution yet 
the most painstaking care. In the discussion of species, plants occupy 45 pages, 
and animals 230. The plant groups considered are Bacteriaceae, Schizophyceae, 
Chlorophyceae, Bacillariaceae, Conjugatae, and certain s plants. Some 
general conclusions in reference to the seasonal changes are stated, conclusions 
that are promised detailed discussion in a later paper. For example, each month 
1s characterized by certain plankton features, dependent upon a certain range of 
hydrographic, thermal, and chemical conditions, and of illumination. There 
'S @ certain range of component species, and a range of numbers of individuals, the 
Proportions varying from month to month, and constituting one of the main 
elements in the seasonal changes of the plankton. Transitions from month to 
month are most profound at seasons of greatest environmental changes, as at the 
times of vernal increase and autumnal decline in temperatures. In general two 
types of plankton were found, the summer and the winter, the vernal and autumnal 
types being only transitions between the two when organisms from both are present. 
The winter plankton is characterized by a small number of species peculiar to that 
Season, and a number of perennial forms; the summer by a larger number of 
summer organisms with the perennial forms. 
In reference to the question whether the plankton of streams differs from that 
Of lakes and ponds, the author states that it may be distinguished from them - 
being a mixed plankton (due to the mingling of planktons from all sources in the 
§ Bor. Gazerre 372472. 1904. 
*Korot, C. A., The plankton of the Illinois River, 1894-1899, with introduc- 
to 
oc MpOn the hydrography of the Illinois River and its basin. Part II. Con- 
Papa organisms and their seasonal distribution. Bull. Ill. State Lab. Nat. Hist. 
* 1c 
le I. pp. vii+ 360. 1908. 
