1922] SEARS—TARAXACUM git 
1909. ROSENBERG (20): compares chromosome conditions of 
T. officinale (vulgare?) and T. confertum, finding in the latter a 
typical reduction from 16 to 8. 
1910. IKENO (9): reports 7. platycarpum Dahlst. to be sexual, 
while 7. albidum Dahlst. (white-flowered) is not. 
1912. SCHORBATOW (21): confirms previous findings for T. 
officinale Wigg. Takes liberal cognizance of cytological variation. 
1913. OSAWA (17): compares in detail cytology of species 
studied by IkENo, agreeing in general with JUEL’s conclusions. 
Finds a variable degree of pairing in pollen diakinesis of T. albidum, 
and besides normal maturation of tetrads, the formation of diads 
by ‘“‘homotypic”’ division. Notes amitosis and supernumerary 
nuclei in pollen; also 16 and 8 chromosomes in sexual, 36 to 40 
in parthenogenetic species. Parthenogenesis probably due to 
hybridization. 
1917. SEARS (23): T. laevigatum as well as T. vulgare shows 
ameiotic parthenogenesis. The former generally gives higher 
percentage of sterile fruits, and both exhibit pollen abnormalities, 
including extrusion of chromatin, amitosis, and defective spindles. 
1920. SToRK (26): T. laevigatum is ooapogamous, and embryo 
sac maturation agrees in general with accounts of JuEL and OsaAWA 
for other ooapogamous forms. Also 26 to 30 chromosomes found, 
but said not to split during the elongated phase which is believed 
to follow diakinesis. 
RELEVANT CYTOLOGICAL PROBLEMS.—As suggested earlier, those 
of chief interest in connection with the present study are (1) the 
mode of synaptic pairing, and (2) cytological variation. 
SYNAPSIS.—The conclusion of workers already quoted (12, 17), 
who have compared ameiotic species of Taraxacum with related 
sexual species, favors the parasynaptic interpretation of reduction 
division. Such conclusion is doubtless justified if the observations 
of prophase conditions upon which it is based are unexceptionable. 
The development of thought upon the subject of synaptic 
pairing has been fully treated by numerous workers, the present 
trends of botanical opinion being fairly crystallized in papers by 
Dicsy (5) and Suarp (24). It is unfortunately true that various 
questions involved hinge upon observations made near the limit 
