200 Johnson. — On the Nursing of the Embryo 
The importance which Griffith attached to the antipodal 
prolongation of the embryo-sac as a character in the diagnosis 
of the Santalaceae was due to the general absence of investi- 
gations on the Loranthciceae. The researches of Griffith him- 
self, of Hofmeister, Van Tieghem, Treub, and Jost have brought 
to light changes in the embryo-sac of different genera of 
Loranthciceae, which are in essential points similar to those 
occurring in the embryo-sacs of genera of Santalaceae , and if, 
as seems probable, the tube of the ovuliferous column ob- 
served by Decaisne in Groutia, one of the Olacineae , be part 
of the embryo-sac, a backward prolongation of the embryo-sac 
would rather serve as an additional point of affinity between 
the Santalaceae , Loranthaceae , and Olacineae , than as a dia- 
gnostic character of the Santalaceae l . Since the preceding was 
in manuscript my attention has been called by Dr. Scott to an 
interesting paper by L. Guignard 2 entitled ‘ Observations sur 
les Santalacees.’ As Santalum was well known the investiga- 
tion was confined mainly to Thesium and Osyris , the species 
being Th. divaricatuin , Rchb., and Osyris alba , L. In both 
cases the flowers were examined from the earliest stage to the 
time of maturity of the fruit. In Thesium the archesporium 
of the ovule is never unicellular, usually of two cells, very 
rarely of more. The coming of the age of the embryo-sac is 
normal in both. The antipodal cells disappear very early 3 in 
Thesium , later in Osyris. not till fertilisation in Santalum. 
Guignard agrees with previous observers in describing the 
hinder part of the embryo-sac (including the placental embryo- 
sac tube) as uni-nucleate, the nucleus in it being the sister one 
of that which gives the endosperm, the two being the result of 
the division of the secondary embryo-sac nucleus. In Thesium 
only one embryo-sac develops, in Osyris all three develop and 
1 A letter from Professor I. B. Balfour cautions me against attaching too 
much importance, taxonomically, to the backward elongation of the embryo-sac, 
as such an elongation, though to a very much less extent, occurs in the root- 
parasites Rhinanthus , Pedicularis , etc. (Hofmeister). 
2 L. Guignard, Ann. d. Sc. Nat. ser. 7, tome ii. pp. 181, 202, PI. 12-14, 1885. 
3 This fate of the antipodal cells helps to explain my great difficulty in seeing 
them in Myzodendron , in the material of which were no young flowers. 
