1918] DEVRIES—MASS MUTATIONS 387 
were much stouter than in the species. During the flowering period 
the height of the plants exceeded that of the species only a little, but 
all organs were much stouter. The internodes were shorter and 
the number of leaves correspondingly larger. Over one-half of the 
whole culture have flowered, the remainder being pulled out earlier 
because unexpectedly the crowding of the plants became dangerous. 
It favors in this mutant, as in the species, the rotting of the 
stems. ae ae 
In September I made the following measurements: height 2 m.; 
leaves of the upper part of the stem 5X15 cm. as compared with 
3-5 X12 cm., in O. grandiflora; petals 4.5 mm.,as compared with 
4.0X4.2 cm.; tube of calyx 4X50 mm. as compared with 2.5 X 
35 mm.; flower buds 1.24 cm. as compared with 0.8 X3.5 cm.; 
apex of petals with two deep incisions, which, in O. grandiflora, are 
often hardly perceptible; lobes of stigma and filaments of stamens 
much thicker than in the species. All these characters were very 
striking on the bed and made the culture one of the most showy of 
my garden, but the ramification was spare in the mutant; in the 
species it is ordinarily very rich. 
The seeds of mut. gigas are about double the size of those of the 
species. I determined the amount of germs per hundred seeds for 
three self-fertilized specimens of my culture of 1916, and found 
75~88 and 89 with an average of 84 per cent. This is only a little 
higher than the average for O. grandiflora itself, 75 per cent (4). In 
the roots of one of the three specimens mentioned the chromosomes 
had been counted by my assistant Mr. C. VAN OVEREEM; their | 
number was 28, as in other instances. 
It should be mentioned that the lorea and ochracea mutants from 
gigas had stout flower buds and large flowers like their sisters, and 
therefore must be considered as O. grandiflora gigas lorea and O. 
grandiflora gigas ochracea. 
O. grandiflora mut. semigigas.—This mutant of 1915 differs 
the same way from the species as did the gigas. I did not find any 
striking difference between the two before the fruits ripened. They 
were stout in gigas, but small and thin in the other mutant, which 
for this reason could not be considered as true gigas, but evidently 
constituted only a semigigas. No fertile seeds could be obtained. 
