MATROCLINIC INHERITANCE 121 
well as in Oe, pratincola, the occurrence of mass mutation is associated 
with a remarkable increase in seed sterility. This very significant 
fact is being made the subject of further study. The degree of seed 
sterility in mass-mutant Oe. Reynoldsii is much greater than in 
Oe. pratincola, and is so marked that otherwise indistinguishable in- 
dividuals, the one stable, the other mass-mutant, can easily be dis- 
tinguished by an examination of the seeds. 
Without going into detailed repetition of data published in the 
former paper on Oe. Reynoldsii, it may be recalled that the wild form 
of the species, f . typica, has given rise to the derivatives mut. semialta, 
mut. dehilis, and mut. hilonga. The f. typica is remarkable in that it 
exists in two morphologically identical phases, one of which is relatively 
stable, whereas the other is mass-mutant, giving rise to polymorphic 
progenies containing all of the mutations enumerated, as well as others 
which have not yet been carefully examined. Mut. semialta was so 
named because the plants of the early cultures, grown in Maryland, 
were about half as high as f. typica. The cultures of the season of 
1 916, grown in Michigan under other environmental conditions, did 
not show so great a disparity in height, but in other respects the forms 
were no less distinct than before. The shape of f. typica is depressed- 
conical, because of the long, widely spreading lower branches, whereas 
mut. semialta has relatively erect lower branches and is therefore some- 
what cylindrical rather than conical in shape. Mut. dehilis is a weak 
dwarf with much reduced foliage. Mut. hilonga was so named because 
its fruits are twice as long as those of mut. semialta, which it closely 
resembles in form and stature. In other respects, however, it will 
be shown that mut. hilonga more closely resembles mut. dehilis, from 
which it springs, than mut. semialta. 
AH the mutations come true from seed, except that mut. semialta 
is capable of giving rise to mut. dehilis, and that the latter may in 
turn give rise to mut. hilonga. Mut. semialta has once thrown a 
mutation which will be known as mut. rigida. It came entirely true 
in a large progeny grown in 1916, and will receive a larger share of 
attention in a future paper. A few other types have appeared in the 
cultures, but it has not been possible to obtain seeds from them. 
Summary of the Cultures 
Figure i is a chart giving the pedigree of all the cultures of Oe. 
Reynoldsii and its mutations that have thus far been grown from self- 
