Br J. jicLUCKiE. 573 



zones probably represent the nueellus and integuments. The gelatinous covering 

 is sticky enough to attach the seed to rough or smooth objects with which it may 

 establish contact. On exposure to dry air or heat it dries slowly, and firmly 

 secures the attachment of the seed. In moist conditions the gelatinous coat 

 readily absorbs moisture, either as vapour or liquid; indeed, such absorption is of 

 considerable importance, for it represents the only source of water to the 

 embryo during its early growth, until its haustorium has penetrated the host's 

 water-tissues. 



The walls of the gelatinous cells consist of two layers, namely, a thick, outer, 

 gelatinous layer capable of swelling, and a thin, spirally twisted, cellulose layer. 

 The cell cavity is narrow, but filled with granular cytoplasm. In nearly every 

 cell a nucleus can be seen. Test-fig. 2 shows a gelatinous cell, from a micro- 

 tome section of material fixed in 1 % ehromaeetie. 



The gelatinous layer of the cell-wall loses its water content very slowly, while 

 the spiral cellulose layer shortens and pulls the seed into closer contact with the 

 surface. The structure and mechanism of the cells are closely parallel to the 

 similar structure which occurs in ArceuthoUum occidentale (Pierce, 1905). 



I have seen attached seeds, which had failed to germinate, still adhering to 

 the surface of branches fully a year after dissemination. The empty husk of 

 the seed, after germination, frequently sticks to the surface for months. 

 Germination. 



The seeds of Notothixos, like those of Loranthus and Arceuthobium, will 

 germinate upon anything', living or dead. Moist conditions, with dimini,shed 

 evaporation, are necessary for the purpose. The gelatinous layer of the walls 

 of the seed-coat cells can then provide the developing embryo with its moisture 

 requirements. The growth of the seedling will depend considerably upon the 

 surface to which the seed has been attached. Any roughness of the surface, or 

 any obstruction in the form of a knot, or leaf, or branch, prevents the excessive 

 elongation of the root. On leaves, the root may gTow until the food reserves in 

 the endosj)erm are exhausted. 



Just before germination the embryo appears as an almost cylindrical mass 

 of tissue, differentiated distinctly into root, hypocotyl, plumule and cotyledons. 

 The root-apex is rounded rather than conical and there is no root-cap. The 

 cotyledons are somewhat pointed, and lie close together. The root and part of 

 the hj'poeotyl fit closely against the endosperm, while the cotyledons are separated 

 from it by a narrow space, which widens as gennination progresses. The 

 endosperm layer, in contact with the embryo, is composed of small, thin-walled, 

 densely protoplasmic, large-nucleated cells, practically free of starch. The outer 

 cells of the endosperm are full of starch. As germination proceeds, a clear 

 space appeal's all round the embryo, so that the dissolved foods from the endo- 

 sperm must diffuse through the fiuid of this space. The peculiar differentiation 

 of the endosperm cells immediately surrounding the embryo suggests the hypo- 

 thesis that they are responsible for the solution of the starch of the endosperm. 



The dermatogen of the embryo is already differentiated, while behind the 

 meristematic cells of the root-apex, and in the cotyledons, the plerome cells, with 

 their elongated, spindle-shaped nuclei, are already organised. 

 The irritability of tJie root. 



The root is not geotropic, but strongly negatively phototropic, always growing 

 towards the more shaded parts of a branch. Frequently very pronoimced curva- 

 tures are completed before the optimum light position is attained by the root 



