28 JOHNSON: FORM OF PIAROPUS PANICULATUS 
one grain was found 88 uv long, only one 76 uw, and only one 74 
u. For the greatest number of grains the long diameters were 
from 38 uw to 70 yu, inclusive. The pollen from short stamens 
measured 34-62 win long diameter and 26-54 u in short diameter. 
he amount of overlapping in size of pollen of the two sets 
of stamens for individual plants was from 0 to 20 wu. For only 
two plants was there no overlapping. For 21 plants the over- 
lapping was more than 6 u.and for some of these it was as much as 
12u. This means that for a large number of plants many of the 
pollen grains in the two sets of stamens were identical in size. 
CONCLUSIONS 
As far as now known Piaropus paniculatus exists as an in- 
completely trimorphic species or as a homomorphic species with 
two sets of stamens differentiated as in the mid-styled form of a 
trimorphic species. _ 
Each of the 37 plants tested with its own pollen either from 
long or from short stamens produced pods with viable seeds, 
thus reproducing in some cases abundantly to what constitutes 
illegitimate fertilization. 
There was no evidence of real and inherent differences in the 
degrees of self-compatibility or of cross- “incompatibility. The 
differences observed may well have involved errors in mani- 
pulation. 
The mid-styled form of P. paniculatus appears to reproduce 
true to form through seed progenies. 
New York BoTanicaL GARDEN. 
BIBLIOGRAPHY 
Darwin, Charles. On the sexual relations of the three forms 
of Lythrum Salicaria. Jour. Linn. Soc. Bot. 8: 169-196. 
1865. 
—. The different forms of flowers on plants of the 
same species. London. 1877. 
Halsted, B.D. Pickerel weed pollen. Bot. Gaz. 14: 255~-257- 
1899. 
Hazen, Tracy E. The trimorphism and insect visitors of Pon- 
tederia. Mem. Torrey Club 17: 259~-484. pl. 14,15. 1918. 
Miiller, Hermann. Die Befruchtung der Blumen durch Insekten. 
Leipsig. 1873. 
