TETRAD AND Empryo-sac MITOSES 73 
arranged sometimes in two rows, and the connecting fibers run 
from one nucleus to the other in such a manner as to recall 
Mottier's* figure of the four nuclei in the upper end of the embryo- 
sac in Helleborus foetidus, and the appearances which one usually 
meets with during the formation of cell walls in endosperms (pl. 
10, fig. 18). 
The prophase of the first division in both pollen and embryo- 
sac-mother-cells is characterized by the stage known as diakinesis 
(of Hácker), in which the chromosome pairs become condensed 
into short, thick rods which lie parallel or become partially twisted 
about or crossed upon each other. The members of each pair 
may fuse at one or both ends, and as the result of more or less 
separation in the middle, may take also the form of rings either 
completely closed, or open at one point. Between these more 
definite forms the chromosome pairs may assume all sorts of inter- 
mediate conditions (Pl. zz, figs. 1, 14, 32, 37, 38). 
In some instances the members of the chromosome pairs may 
be separated from each other for a considerable distance, and the 
linin strands which unite their ends, may under such conditions be 
seen with the greatest clearness )۸ 9, fig. 27, a). In Galtonia 
candicans, according to Schniewind-Thies + the same behavior has 
been noted. 
The formation of the rings takes place much more completely 
and earlier in 4Asperula in which genus also the condensation of 
the large loose rings into small thick ones may be followed with 
ease (pl. 9, figs. 1 and 2). The appearances so presented recall 
the figures of vom Rath + of the chromosome rings in Gryllotalpa 
excepting, however, that no phenomena of tetrad formation (in 
the sense of the zoologists) may be observed. 
During the prophase of this division the number of chromo- 
somes may in these forms quite easily be determined and with 
a high degree of certainty has been found to be oxe-half the usual 
number in the sporophyte. The reduced number, which has been 
determined by counts, not only in the prophases, but in the ana- 
a das Verhalten der Kerne, etc. Jahrb. wiss. Bot. 1897. 
e Reduction, der Chromosome Zahl und die ihr folgenden Kerntheilungen in 
den nie der Angiospermen. Jena, 1901. 
} Zur Kenntniss der Spermatogenese von Gryllotalpa vulgaris. 
1892, 
Arch. Mic. Anat. 
