Tripsacum australe, the only native South American 
species of the genus, is found from Colombia to Bolivia, 
Paraguay and Brazil. It is very variable in habit. Little 
is known about its cytology. Graner and Anderson(1944) 
investigated a large robust clone from Mato Groso, Brazil, 
which had eighteen pairs of chromosomes and differed 
from all other species of T'ripsacum in lacking terminal 
knobs on the chromosomes. Since further information 
regarding this species seemed desirable, a study was made 
of Colombian plants. These are smaller, with sessile 
paired staminate spikelets and they usually set fertile 
seeds. 
Material of both these clones was collected for this 
study by W. H. Hatheway at the Estacion Experimen- 
tal **’Tulio Ospina’’ at Medellin during the summer of 
1956. Inflorescences of the selected clones were fixed in 
the field in a freshly prepared mixture of three parts of 
95% ethyl alcohol and one part of glacial acetic acid. 
Aceto-carmine squash technique was followed through- 
out the study. 
OBSERVATIONS 
Tripsacum lawum Nash 
All of the stages of meiotic division, starting at pachy- 
tene, were found. Considerable difficulty was encountered 
in the identification of the chromosomes, because of the 
extremely irregular chromosome behavior at both pachy- 
tene and diakinesis. However, after a number of cells 
had been studied, it was concluded that this form of 
Tripsacum has 54 chromosomes and is a triploid. This 
conclusion was finally confirmed by chromosome counts 
of the tapetal cells in the anthers. 
Not a single microsporocyte showed clearly all the 
chromosomes of the three chromosome sets. Through a 
number of separate measurements of different cells at 
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