1900 | CURRENT LITERATURE 365 
and forming a tissue which supplements the endosperm. The embryo is also 
somewhat peculiar and suggestive. The failure to develop a suspensor is 
thought by Professor Campbell to be associated with the complete investment 
of the embryo by the endosperm. Two types of segmentation of the young 
suggestive of the first divisions of the fern embryo. e cotyledon is 
exceedinglylarge as compared with the stem and root, the last organ appear- 
ing late and being rather lateral in origin, as in Lysichiton and Pistia. 
One of.the peculiarities of Dieffenbachia is that the single archesporial 
cell divides transversely very unequally, the outer cell being the larger and 
becoming the embryo sac. The inner cell may divide once or not at all. 
The embryo sac in its development encroaches upon the whole of the nucel- 
lar tissue and finally is in contact with the inner integument. A nucellar 
cap, however, remains at the micropylar end of the sac, and its cells enlarge 
an divide, forming a somewhat permanent tissue, and suggesting the condi- 
tion of things which Smith has found in Pontederiacee and Merrell in 
Silphium. 
The characteristics of the group which have been developed so far, and 
which the author regards as primitive, are the axial ovule, the early develop- 
ment of a solid endosperm, the great development of the antipodal cells, and 
the absence of a suspensor.—J. M. C. 
A NEW GENUS of the Volvocacee from the streams of central Illinois, 
has been described by Kofoid*s and named Platydorina. It forms a flat horse- 
shoe-shaped colony of sixteen or thirty-two cells, the plate being somewhat 
twisted into a left spiral. The rounded side of the outline is the anterior 
end, and the portion corresponding to the heel of the horseshoe is prolonged 
into three or five tails, hence the name of the single species, ?. caudata. The 
contents of the cells are bright green, and each has a pair of cilia and gen- 
erally the red pigment spot. The tails are formed of intercellular gelatin- 
ous matter, and they, with the peculiar twist of the colony, present the most 
Prominent specific characters. No method of sexual reproduction has been 
discovered. 
late, in such a regular manner that every alternate cell has t : 
Pigment spot uppermost to the observer, while the other cells present the 
= ag Sa On Platydorina, a new genus of the family Volvocide, from the 
*kton of the Illinois river. Bull. Ill. State Lab. of Nat. Hist. 5, 1899. 
