32 



DE. E. K. GATES— CONTEIBUTIOX TO A 



Crustacean larvae, it appears from the results of Boreri (1905) and Artom (1911) that, 

 altliougli doubling in tlie number of chromosomes in the race is followed by corre- 



sponding increase in the volume of the nuclei and cells, yet a regulation in the mmiherof 

 cells takes place, so that the resulting larvae are not of gigantic size. This appears at 

 jn-esent as an interesting difference between plants and animals, there being apparently 

 no marked diminution in the number of cells in certain at least of the tetraploid races 

 of plants. It seems not improbable that this lack of regulation in cell number in 

 plants may be due to the greater thickness and rigidity of the cell- walls in plant embryos 

 and tissues, so that the controlling action of the young organism as a whole is not able 

 to express itself in re-arranging the cells as formed, in such a way that fewer and larger 

 cells will compose the growing embryo. 



O. gigas also exhibits a wider range of variability in leaf-shape than any other of the 

 mutants from 0. Lamarchiana. PL 3. fig. 32 represents a typical rosette, but in a large 

 culture the leaf-blades range from practically orbicular to narrowly linear. In each 

 individual, however, all the leaves are usually of the same shape within narrow limits of 

 fluctuation, though occasional rosettes show considerable variation in. this regard ; nor 

 have I observed the same succession of ontogenetic stages of the rosette as in 

 O. Lamarchiana^ and the other forms already described, in the 0. gigas from DeVries's 

 cultures. So far as I have observed in this race of 0. gigas^ leaves corresponding to 

 type (1) and type (2) in O. Ziamar chiana and O. laevifolia do not occur, at least under 

 ordinary conditions of culture. In 1909 I grew a culture of 434 plants of O. gigas, 

 constituting the sixth generation from the original mutation of DeVries from 

 O. Lamarchiana. PL 3. fig. 33 shows the rans^e of variation in leaves taken from the 



J-,. ^^ ^^*^„^ .^^v. --— _, 



mature rosettes. In each rosette all the leaves belonged to one type. PL 3. figs. 34, 

 36, 36 & 37 represent individual rosettes, the range of variation being astonishing. 

 Schouten (1908) attempted to isolate six types from the series of forms, but states that 

 the offspring of any one type showed the whole range of variation, so that this could 

 not be done. On account of the strongly biennial character of O. gigas only four plants 

 of my culture came into fiower. From these I raised 48 plants in the following year, 

 but the numbers were not large enough to test the inheritance of this remarkable 



range of variations. They indicated, however, that the offspring of each plant tended to 

 resemble its parent, though occasional rosettes departed from this rule *. 



In PL 3. fig. 38 the buds of O. gigas are shown, two-thirds natural size. As will be 

 seen, they are very much larger than those of O. lata (PL 3. fig. 43, left), w hich they most 

 resemble. Cytological examination showed that the particular individual whose buds 

 are here represented possessed 28 chromosomes. This plant produced much pollen, 

 which was used in makinsj several crosses. 



o 



An interesting form which frequently appears in families of O. gigas is a dwarf, 

 O. gigas nanella. It is photographed in PL 3. fig. 39 on the same scale as the previous 

 rosettes, to show its comparative size. It has not the O. nanella leaf-shape, but is 



* It ia probable that the meiotic chromosome distributions arc fundameutally coucerned in the determination of 

 these various types. . . 



