1904 ] CURRENT LITERATURE 481 
WILLIAMS,” in continuing his studies in the Dictyotaceae, has described 
the gametophyte generation of Dictyota dichotoma, dealing with the develop- 
ment of egg and sperm, fertilization, ata ion of the fertilized egg, a 
parthenogenesis. The oogonia and antheridia are developed simultaneously 
in fortnightly crops, each crop being initiated a little before the lowest neap 
tide, and reaching maturity about the period of the highest varies spring 
tide. A regular succession of crops continues thus from July to the end of 
October. The eggs are hietated for fertilization, and those not bccstlinea 
within half or three-quarters of an hour become invested by walls and give, 
rise to parthenogenetic embryos. The oogonium and antheridium are pro- 
duced by the increased growth of surface cells, and after cutting off a stalk- 
cell they form respectively a single egg and over I500 sperms. All the 
divisions of the antheridium are homotypic, and there are sixteen chromo- 
somes. The sperm has a lateral cilium, and there may be a second very 
ane seduced cilium, but it is difficult to demonstrate. The eye-spot is very 
small,and instead of being at the age of the cilium is generally near the 
anterior end of the beak. After fertilization thirty-two chromosomes appear, 
divides, and as the two centrosomes separate the two spindle cones also 
diverge, until finally they form a normal spindle, In parthenogenesis the 
nucleolus breaks up into chromosomes, leaving no residual nucleolar matter 
to be extruded into the cytoplasm, as occurs in other mitoses. The mitotic 
figure is very irregular and multipolar; there is no nuclear membrane, and 
a cluster of nuclei is formed, each containing one or several chromosomes. 
These separate into two or more groups, and walls are formed between them. 
The process may go on a little further, but very soon it stops and the embryos 
die. Comparing ie germination with parthenogenesis, it is gs Cate 
that the entrance of the sperm into the egg causes a centrosome and radia- 
tions to appear in a cytoplasm, renders the metabolism of the aia far 
more active, introduces into the mitosis a directive influence that is com- 
pletely absent from the saaotnaaang ae and prevents the early disap- 
pearance of the nuclear membrane.— 
MASSEE®* has published an ee tele comin and suggestive paper on 
the origin of parasitism in fungi. The author refers to the experiments of 
Pfeffer and of Miyoshi on chemotaxis, and then shows by his own experiments 
that the germ tubes of parasitic fungi in general are attracted by decoctions 
of their respective host plants. Thus Macrosporium Tomato and Clado- 
sporium fulvum are attracted by decoctions of tomato leaves, Cercospora 
medonis is attracted by a decoction of cucumber leaves, etc. Obligate para- 
sites are attracted eee by the cell sap of the plants upon which they are 
79 WILLIAMS, J. LLoyp, Studies in the Dictyotaceae. II. The seh of the 
gametophyte generation. gem of Botany 18: 183-204. pls. 12-74. 
3° MAssEE, G., On the origin of parasitism of fungi. Phil. path Roy. Soc. 
London B, 197: 7-24. 1904. 
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