The transmission of hereditary characters from parents to pro- 
geny is exclusively the function of chromosomes in the nucleus of certain 
specialized cells: in plants, the sex cells of flower bud tissue (pollen cell 
nuclei and egg nuclei). When it comes to the number of chromosomes, the 
sex cell nucleus of an individual carries a complement of one-half the number 
available in any other body cell. Number and character of these chromo- 
somes remain constant, with few exceptions, throughout the life of the 
individual. For example, in the genera Cattleya, Laelia, Brassavola, Sophro- 
nitis and Cymbidium, the somatic (body cell) number is forty chromo- 
somes, one set of twenty obtaining from each parent. The overwhelming 
majority of plants in the above genera fall in this category and are techni- 
cally indicated as diploids because the somatic number is twice the meiotic 
(sex cell) number. Under certain very unusual circumstances (such as by 
natural accident or brought about by the extraordinary actions of certain 
powerful drugs, X-rays, fissional radiation, or extreme temperatures) the 
chromosome number occasionally may be caused to change. If in the body 
cell the number rises to sixty, a triploid plant individual is the result. 
If the result is a complement of eighty chromosomes, the indi- 
vidual is called a tetraploid. A pentaploid would have five sets of the 
meiotic number or one hundred chromnsomes. Triploids, tetraploids, penta- 
ploids etc., in other words individuals with more than forty chromosomes 
in their somatic count are called, collectively, polyploids. 
Counting of chromosomes is a painstaking, time consuming 
eperation that can only be carried out with specialized techniques and at 
highest magnifications. Yet, it is merely one of several devices of funda- 
mental research we are applying in the year-around laboratory development 
of superior orchids for the future. 
In orchid breeding, the number of chromosomes possessed by a 
plant is, among others, a primary cytological factor deciding the qualifica- 
tions of that plant to serve as a worthy parent or stud. Experience accumu- 
lated from intense experimentation over the years indicates unmistakably 
that polyploidy, or the presence of more than the number of chromosomes 
