1918] CURRENT LITERATURE 79 
to be related to the character of the natural habitat of the species in question. 
Thus Salix sp. (probably nigra) stands at one end of the series and shows no 
injurious effect even when the oxygen of the atmosphere is entirely replaced 
by either nitrogen or carbon dioxide. At the opposite end of the series stands 
Opuntia versicolor, growth of roots ceasing with an atmosphere containing 
50 per cent carbon dioxide, while Coleus Blumei is comparable to it, showing 
injury and ultimate death with the addition of 25 per cent nitrogen to the soil 
atmosphere. Of the other species at Heliotropium peruvianum was closely 
comparable to Opuntia, while Nerium oleander and Prosopis velutina prove 
nearly as resistant as Salix. The net seem to indicate that plants growing 
naturally in well drained soil are much more sensitive to the composition of 
the soil atmosphere than those from swamps and poorly drained habitats.— 
Gro. D. FULLER 
Embryo of Aucuba.—Patm and RutGERS* have settled the question of 
apogamy in Aucuba japonica, which has been under suspicion for 40 years. 
They bagged 300 pistillate flowers and not a single fruit formed, while 600 
isolated pistillate flowers produced normal fruit after artificial pollination. It 
is thought that E1cHLEr’s original suggestion of apogamy probably came from 
the fruiting of an isolated pistillate plant which had developed staminate 
flowers, since the authors have repeatedly found staminate flowers on pistillate 
plants. Staminate plants have also been observed to produce pistillate flowers. 
The flowers open about the time of megaspore formation, and the embryo 
sac reaches the fertilization stage about 4 weeks later. The solitary megaspore 
mother cell becomes deeply placed by the extensive development of parietal 
tissue. The behavior of the 4 megaspores is usually quite normal, but in one 
case the 2 megaspores nearest the chalaza were found in division. The develop~ 
ment of the gametophyte is normal, but stages in endosperm formation were 
not obtained. The chromosome numbers were determined to be 18 and 36. 
mS 
— 
Disease resistance.—JonEs* has published a summary of his results in 
securing a race of cabbage resistant to the “yellows.” Some of the funda- 
mental questions involved in resistance were considered. The difference 
between susceptible and resistant plants was found not to be due to any super- 
ficial obstacle, but to the different relations of the interior cells of the host and 
parasite. ‘The resistant tissues have the ability to restrain the development 
of the parasite to a greater degree than do the susceptible and so give time for 
protective cork formation.” It was shown also that resistance is clearly 
inheritable, not as a single character, but as a complex of a number of heritable 
* Pata, By., and Rutcers, A. A. L., "The embryology of Aucuba japonica. Rec. 
Trav. Bot. Néerland. 14:119-126. figs. 12. 1917. 
* Jones, L. R., Disease resistance in cabbage. Proc. Nat. Acad. Sci. 4:42-46. 
18, 
