93 
Teratological Seedlings. II. 
Stramonium , and Acer pseudoplatanus, and also by Braun (1) in Coelobogyne 
ilicifolia , Euonymus latifolius , and a number of other species. In some 
instances the seedlings were fused together for only a short distance ; others 
exhibited complete fusion of the hypocotyl and root, the origin however 
being indicated by a more or less deep cleft in the hypocotyl ; others, 
again, presented the appearance of normal tetracotylous seedlings. In no 
case, however, were the cotyledons fused as in the Centranthus seedling. 
Two possible explanations of the twinning phenomenon present them- 
selves : 
(a) We may assume that the early divisions of the embryo initial are 
quantitative in character, and that in this case the two daughter-cells have 
been separated, each developing into a complete seedling without, however, 
the connexion between the two being completely severed. 
(b) It is possible that two distinct embryos may have been produced 
either in the same or in different embryo-sacs, these embryos becoming 
more or less completely fused together. 
That the early divisions of the embryo are quantitative in character in 
the Coniferae seems to be clearly demonstrated by the fact that each cell 
of the embryo tier may independently produce an embryo, although usually 
only one of these develops to maturity, whilst in those forms such as Sequoia 
in which the embryo tier consists of one cell only this may divide by 
a longitudinal wall, and if the daughter-cells separate, two embryos may be 
produced (Coulter and Chamberlain (4) ). Among Angiosperms only one 
case of this type has been reported. A. Braun (1), apparently quoting 
Hofmeister (8), stated that in Loranthus europaeus the terminal cell of the 
proembryo divides by two longitudinal walls, laid down at right angles to 
one another, and that each of these cells after further divisions may form an 
embryo. Usually, however, only one embryo matures, the production of two 
or more embryos being a rare occurrence. 
Whilst in these cases fusion between the sister embryos is not recorded, 
such twinning is not unknown in the Animal Kingdom as a result of the 
partial separation of the early blastomeres in holoblastic ova. 
It seems not impossible, therefore, that the ‘ twinned ’ seedlings of Cen- 
tranthus and other forms may be produced in the manner suggested. 
The second possibility remains that the * twin ’ may have arisen by the 
fusion of two distinct embryos, these arising either in one embryo-sac or in 
separate embryo-sacs, or in distinct ovules which have undergone fusion. 
In this connexion it is interesting to note that Hofmeister records that in 
Viscum album the embryos produced in the one embryo-sac may fuse by 
their cotyledons. Braun also suggests that the twin seedlings of Coelobogy?ie 
may arise from the fusion of two distinct embryos, basing his suggestion on 
the facts that two or more embryos have been observed in one embryo-sac, 
and that the abnormal seedlings form a series leading from types in which 
