Johnson . — 'On A rceuihobium Oxycedri . 149 
A. Oxycedri a placenta formed of the modified apical part 
of the floral axis bearing two imbedded ovules reduced to 
their simplest condition, that of unicellular hypodermal arche- 
sporia, one mature embryo-sac being developed from each of 
the two archesporial cells, 
4. The Fruit of A. Oxycedri. 
It is known that an interval of fourteen months elapses 
between the formation of the female flower and its dehiscence 
as a ripe fruit. Unfortunately, the material at my disposal 
was collected at one time, probably the middle of November. 
Mr. Carruthers very kindly gave me some dried material of A, 
Oxycedri from the Herbarium of the Natural History Museum ; 
it was unfortunately in the same stages as my spirit material, 
as was also some in the Herbarium at Kew which Professor 
Oliver was so good as to look through with me. It was 
so well preserved that nearly all the details seen in the 
spirit material could be verified in it. 
Between the oldest pollinated flower and the youngest fruit 
there is a difference of a year. I cannot say whether 
Arceuthobium shows any migration of its embryo-sacs or 
embryo such as Griffith, Hofmeister, and Treub have seen in 
different Santalaceae and Loranthaceae. It would be still more 
interesting to know whether the two embryo-sacs have each 
an embryo and endosperm, whether the two sacs become ever 
fused, whether if there are two endosperms they become one ; 
phenomena observed by Van Tieghem in Vis cum album. 
There is one important respect in which the reduction in 
Arceuthobium is much less than in other Loranthaceae. While 
in other Loranthaceae the papilla of the ovary when present 
becomes fused with the wall of the ovary so that the gynaeceum 
is a solid body even before fertilisation, this does not happen 
in Arceuthobium. The ovarian papilla does not at any time 
become fused with the wall of the ovary. 
In the ripe fruit the apical part of the papilla forms a sort 
of calyptra to the radicle, and the basal part is thrust to one 
