No. 463.) STUDIES ON PLANT CELL.— VI. 469 
zygospores of Conjugales on germinating present similar events. 
The teleutospore and basidium are probably also the seat of 
chromatin reduction (Blackman, :04b) in the formation of 
spores either directly or through the promycelium. The ascus 
holds a position at the end of a sporophyte phase which suggests 
a similar relation in this group of fungi. Chromosome reduction 
may also be expected in the tetraspore mother-cell of the Rho- 
dophyceze, as in Dictyota, but this subject has never been inves- 
tigated. There are occasional red algze in which the tetraspores 
are sometimes borne on the same plant with the sexual organs, 
conditions which may be difficult to explain on the theory that 
the tetrasporic plant is a sporophyte. Thus Spermothamnion 
turneri on the American coast frequently bears both procarps 
and tetraspores on the same plant, and I have also seen cysto- 
carpic plants of Ceramium rubrum some of whose branches con- 
tained tetraspores. Lotsy (:04a) also reports similar conditions 
in Chylocladia kaliformis. The other extremely varied methods 
of spore formation (zoöspores, conidia, etc.) in the thallophytes 
do not concern the present discussion: They seem to have no 
fixed place in the life history and there is nothing to indicate 
any relation to reduction phenomena, although we actually know 
nothing about the chromosome history among, these lowly forms. 
The importance of sporogenesis as a critical period in the life 
history of higher plants became at once apparent with the dis- 
covery that fertilization doubled the number of chromosomes in 
the nuclei of the sporophyte phase and that the double number 
was reduced during sporogenesis. As stated in our account of 
gametogenesis, these facts were first established for a number of 
spermatophytes by the work of Strasburger ('84, '88, and 94), 
Guignard (84, '85, and '91), and Overton (93 a and b). Guig- 
nard (’91) presented for Lilium martagon the first complete 
account of the number of chromosomes in the life history of a 
plant, and his results were also established independently by 
Overton ('93 a and b). Then followed confirmatory arestiga 
tions among the bryophytes in the work of Farmer ('94, '95 a, 
b, c) and in the pteridophytes by Strasburger (94, p. 294) for 
Osmunda. Since 1895 the investigations among the spermato- 
phytes have so multiplied that we know the number of chromo- 
