APPENDIX. BOOK II. 
959 
After the two cotyledons of the developing embryo have made their appearance, an 
outgrowth, similar to that in Welwitschia, is produced at the base of the hypocotyledonary 
stem ; but in Gnetum its position relatively to the planes of the cotyledons is not fixed, as 
in fVelivitscbia, the point at which it is formed being determined by the action of gravity, 
so that it always developes on the under side of the hypocotyledonary stem. Further, the 
organ is larger in Gnetum, and the pith and vascular tissue take part in its formation, 
whereas in JVelavitschia it is derived only from the cortex and epidermis of the hypocoty- 
ledonary stem. 
In the three genera of Gnetacese this organ is developed for the transfer of nutritive 
material from the seed to the seedling, the size of the organ being proportional to that of 
the seed and to the quantity of reserve material. 
Page 534, hne 2 from bottom (note). For ' Eilcher ' read ' Eichler.' 
Page 574. The morphological significance of the ovule. See above, note on the 
female flowers of Coniferae. 
Page 576. On the development of the ovule of the Loranthaceae, see Treub, 
Observations sur les Loranthacees, Ann. d. Jardin botanique de Buitenzorg, vols. 2 and 3, 
Leyden, 1882. 
In Lorantbus sphcerocarpus there is, according to Treub, a central placenta which 
bears three or four free lateral segments ; these Treub regards as rudimentary ovules. In 
each of these several embryo-sac-mother-cells (archesporial cells) are formed, but only 
one embryo-sac becomes fully developed : it is developed from the uppermost cell of the 
row formed by the division of the mother-cell. 
In the Viscum album and articulatum there is no placenta and no ovule, but the 
embryo-sacs are developed in the tissue of the carpels ; in V. album there is a relation 
between the number and position of the embryo-sacs and the carpels, but in V. articulatum 
this is not the case. In spite of the degradation of these plants, the mother-cells of the 
embryo-sacs are nevertheless of hypodermal origin as in the other Angiosperms. 
Page 578, Hne 8 from top. For ^ maculatam' read ' maculatum.'' 
In addition to the instances here given of deviation from what may be regarded as 
the typical mode of development of the embryo-sac, it m.ay be added that in some cases it 
is the uppermost of the cells of the row formed by the division of the archesporial cell 
which developes into the embryo-sac, e. g. Loranthus sphxrocarpus (Treub), Pyrethrum 
balsaminatum (Marshall Ward), Agraphis patula (Treub and Mellink). For the most 
recent researches on the embryo-sac of Angiosperms, see Guignard, Ann. d. Sei. Nat., 
ser. 6, t. XIII, 1882. 
Page 580. The Synergidae. Strasburger (Bau und Wachsthum der Zellhäute, 
1882) considers that the longitudinal striation (Filiform Apparatus of Schacht) mentioned 
in the text is due to the presence of delicate canals which are filled with protoplasm ; the 
body of the Filiform Apparatus is probably not protoplasmic. 
Page 588. Development of the Embryo. See also Rech, embryol. sur VOrchis 
maculata, Monteverde in Melanges Biologiques de I'Acad. Imp. de St. Petersbourg, 1880; 
Guignard, Rech, d'embryogenie vegetale comparee, Ann. d. Sei. Nat., ser. 6, t. XII ; and 
Treub, Notes sur I'Embryon, le Sac embryonnaire, et I'Ovule, in Ann. d. Jardin bot. de 
Buitenzorg, III, 1882. 
Treub's researches refer to PtrUtylus grandis and to A'vicennia officinalis. "With 
regard to the former he finds that the embryo remains at first rudimentary, whereas the 
suspensor grows rapidly and until it projects through the micropyle ; it then branches, 
and the branches become closely applied to the placenta. At this time the embryo begins 
to develope, and there is no doubt that it does so in consequence of the supply of nutritive 
material which is absorbed from the placenta and transmitted by the suspensor. These 
observations confirm Treub's previous conclusions as to the function of the suspensor in 
Orchids. 
With regard to A'vicennia, Treub's observations complete our knowledge of this 
curious ' viviparous ' plant long ago described by Griffith (On the development of the 
