92 BOTANICAL GAZETTE ; [FEBRUARY 
been superseded in the more mature rosette by leaves of a different 
form, but that the sharp distinction between the variation and the 
typical form has not been obscured. The occurrence of so interest- 
ing a variation in Lexington C led to a careful examination of the 
strain for evidence of mutability. 
A second sowing of the same seed on good soil resulted in a 
progeny of 720 seedlings from 1000 seeds. As soon as the seedlings 
were well rooted, they were transplanted to square seed pans in which 
they were widely enough spaced to allow of unimpeded growth for 
a month or six weeks. This system was followed in all subsequent 
work. Of course, the seeds were invariably sown on sterilized soil. 
After the seedlings were transplanted, the pans were frequently 
examined for mutations, and all plants which were noticeably 
divergent from the mass of the culture were marked for preser- 
vation. Among the 720 seedlings of the second sowing, there were 
only 4 round-leaved plants. Since the mass of the culture was 
uniform, and the round-leaved plants constituted an absolutely 
discontinuous variation from both the typical form and one other 
pronounced variant which occurred in the culture, it was concluded 
that they were probably mutations. In the following pages the 
round-leaved type is called O. pratincola mut. nummularia.” 
In order to show the discontinuity between typical O. pratincola 
and mut. nummularia, photographs of two of the seed pans In 
which this mutation occurred are reproduced as figs. 5 and 6. At 
the time the pans were photographed, the plants were about as 
far advanced as nos. 1-4 in fig. 3. Comparison of the figures will 
7 The writer has suggested (Amer. Jour. Bot. 1:237. 1914) that mutations of 
experimental origin be given trinomial names such as O. pratincola mut. nummularia, 
in order to avoid confusion with names which must be given consideration in floristic 
works. A trinomial nomenclature has the advantage over the binomial system pro- 
posed by Gates (Trans. Linn. Soc. London II. Bot. 8:10. 1913) in that the parallelism 
of mutations occurring in different species may be indicated by the use of the same 
mutational designation. For example, a convenient way to show the parallelism 
between the mutations of O. Lamarckiana and those of O. biennis would be to call 
them O. Lamarckiana mut. semigigas, O. biennis mut. semigigas, etc. The trinomial 
used in this way need imply nothing as to the specific, varietal, or formal rank of a 
mutation, but only the manner of its origin. Nevertheless, for the sake of avoiding 
confusion, it would be well not to give any mutation a name which had poe 
been used in any subspecific category within the species which had given rise to 
mutation. 
