no 
PACIFIC SCIENCE, Vol. XVIII, January 1964 j 
TABLE 5 
Mean Chromosome Configurations at Metaphase I of Meiosis in PMCs of 
Between-Section Hybrids of Phalaenanthe and Ceratobium, 2n = 38 
HYBRID 
MEAN CONFIGURATION 
PER PMC 
NUMBER OF PMCS 
OBSERVED 
D. superbiens (natural hybrid) 
2.04i-f-17.80 2 +0.12 3 
25 
D. phalaenopsis x D. undulatum 
2.34i+17.762 
29 
D. phalaenopsis x D. gouldii, #1 
3.87i+17.07 2 
25 
D. phalaenopsis x D. gouldii, #2 
6.48i+15.76 2 
25 
D. phalaenopsis x D. tokai 
2.42i+17.732+0.04 3 
26 
D. phalaenopsis x D. taurinum 
I.OO1+I8.5O2 
24 
D. phalaenopsis x D. johannis 
0.16i+18.92 2 
100 
D. phalaenopsis x D. veratrifolium 
2.50i+17.702+0.033 
30 
Meiosis in W ithin-Section Hybrid of Latourea 
The single plant of D. atroviolaceum x D. 
macrophyllum (Figs. 19, 20) was a rare and 
unexpected hypodiploid with 2n == 37. Meiotic 
behavior was comparable to that often en- 
countered in trisomics (Tables 7, 9, Fig. 32). 
Twenty-four out of 25 PMCs examined showed 
one trivalent plus 17 bivalents and only 1 
PMC showed 18 bivalents plus a univalent. 
A few bivalents were more or less hetero- 
morphic. Trivalents were either V-shape or, as 
can be seen in Figure 32, a chain of three. At 
anaphase I, the chromosomes of the bivalents 
separated regularly to both poles, while the tri- 
valent usually separated two for one. The prod- 
ucts of meiosis were tetrads. 
Meiosis in Between-Section Hybrid of Cera- 
tobium and Latourea 
The irregular meiosis in D. lasianthera x D. 
macrophyllum ( Fig. 21) revealed variations in 
number of bivalents from 14 to 7 with a mean 
of 10.8 and univalents from 10 to 26 with a 
mean of 16.3 (Table 8, Fig. 33). Nearly all 
bivalents were heteromorphic. Univalents were 
of variable size, and scattered in and around the 
loose metaphase plate. 
At anaphase I, the bivalents separated toward 
both poles, while the univalents often lagged 
between the two anaphase groups, and ulti- 
mately the entire group was reconstituted into 
restitution nuclei. Dyads and dyads with micro- 
cytes were, therefore, common products of 
meiosis. A few triads, tetrads, and tetrads with 
microcytes were also observed (Table 9). The 
relatively high frequency of triad formation sug- 
gests that restitution also occurred at the second 
division. 
Meiosis in Between-Section Hybrid of Phalae- 
nanthe and Latourea 
Meiosis in D. phalaenopsis x D. New Guinea 
(Figs. 22, 23) was highly irregular. The number 
TABLE 6 
Chromosome Configurations at Metaphase I of Meiosis in PMCs of 
Tetraploid Hybrids, 2n = 76 
SECTIONS INVOLVED 
HYBRID 
CHROMOSOME CONFIGURATIONS 
U U 2i 2± 2i 
38o 37 2 362 35 2 34 2 33s 32 2 
2i 2i 2i 
Ceratobium x Ceratobium 
Phalaenanthe x Ceratobium 
D. stratiotes x D. undulatum 12 
D. phalaenopsis x D. gouldii 25 
15 
