AND ON POLYEMBRYONY IN THE HIGHER PLANTS. 31 
soon as the embryo has broken through those upper cells with 
the albuminous body. 
The occurrence of several embryo-sacs, and the formation of 
embryos in them, takes place therefore in the young fruit of 
Viscum, as we have already seen, not unfrequently ; but it is not 
long before one of these embryos, with its enveloping embryo- 
sac, presents a distinct development; while the other, or even 
tue two which occur in proximity, remain behind in their 
development, and are at last entirely abortive. Thence it 
comes to pass that in ripe seed of Viscum several embryos must 
be of exceedingly rare occurrence, if indeed they have ever 
actually been met with. In the summer just passed I have 
been able to observe several embryo-sacs, with their young em- 
bryos, as far as the first half of July; about this time the pre- 
dominant development of one constantly occurred, if it had not 
already taken place even in June. From the commencement 
of August the examination of the seeds of Viscum becomes very 
difficult from the formation of viscin; but now fine cross sec- 
tions may be employed, and these examined even with glasses 
of the highest power, to arrive at a conviction that only the one 
embryo, imbedded in its albuminous body, arrives at deve- 
lopment, and that its formation can by no means ensue from a 
cohesion of several. The occurrence of several rootlets in the 
germinating seed of Viscum is by no means rare, and therefore, 
if this phenomenon were explained by a cohesion of several em- 
bryos, we should find those cohering embryos in the ripe seed 
to be not at all unfrequent. The fine horizontal sections of 
the mature seed show, however, quite distinctly, that the embryo 
is simple, and constantly possesses two cotyledons of usual 
structure ; it is surprising, however, that the cauliculus exhibits 
almost from the radicular end two more transparent places in the 
cross section which are formed by somewhat large latticed cel- 
lular tissue, and are prolonged even into the two cotyledons ; 
perhaps these led to the adoption of the supposition that the 
embryo is here formed by the cohesion of several. 
In conclusion, I have to acknowledge my obligations to the 
royal gardener, L. Fintelmann, who kindly furnished me during 
_ the summer with the requisite quantity of mistletoe-plants. 
