10 THE IXHUNTHACEAE OP AUSTRALIA, 1., 



assumed as an explanation of synangial states by various writers, but it can only 

 rarely be proved on gi-ounds of comparison that fusion of sporangia bas actually 

 taken place, and the best evidence of it comes from the Angiosperms. Thus the 

 fusion of the ovules, leading indeed to obliteration of their identity, occurs in 

 certain species of Loranthus, and comparison leaves little doubt that the sunken 

 embryo-saes represent the individual ovules, the identity of which is lost as re- 

 gards external forms." 



On this same subject Worsdell (Principles of Plant Teratology, i., p. 93) 

 ■r|uotes Treube, who "describes a case in which Loranthus sphaerocarpiis, the fer- 

 tilized ovum divides by a vertical wall, but the sister-cells develop together into 

 a single proembryo, consisting of a double row of cells. The case of imperfect 

 twins, in which the lower part of the structure is undivided while the upper is 

 separated into two similar parts, represents at once the simplest case of fasciation 

 in existence and also the phenomenon which most easily and clearly explains it, 

 illustrating as it so well does the result of the compromise between the two ten- 

 dencies towards unification and separation respectively. It is a by no means 

 uncommon phenomenon for two embryos or young seedlings to appear more or 

 less intimately fused together." 



Griffith (Trans. Linn. Soc, xviii., i., p. 82) refers to the plurality of em- 

 bryos in some Indian species of Viscum. Also J. D. Hooker (Fl. British India, 

 v., 223) says, "Embryo in fleshy album, solitary or 2 in each seed." 



Double embryos have also been found in Viscum album L., the well known 

 European mistletoe, and attention has been recently drawn to it by Dom Ethel- 

 bert Home (Journ. Bot., liv., 1916, p. 292) who says, "There appear to be two 

 kinds of mistletoe seeds — those that produce but one radicle and those that pro- 

 duce two or more. The former are oblong in shape and the latter triangular. 

 In the paper by the late Dr. Bull of Hereford on Viscum album (Trans. Wool- 

 hope Club, 1852-65, p. 312) he states that out of 36 seeds taken at random, 25 

 had a pair of radicles. I put 30 seeds, also taken haphazard, in a patch on the 

 trunk of a plane-tree. Three of these were lost, and of the remaining 27, two 

 radicles came from 19, which is almost exactly the same proportion as in Dr. 

 Bull's experiment. But where he obtained only 4 seeds with single radicles out 

 of 36, I grew 7 out of 27 — a very much larger proportion. Also in the older 

 oxperiment 7 seeds had 3 radicles, whereas I had only 1." 



Brittlebank (These Proc, xxxiii., 1908, 650, fig. xxx.) depicts a double 

 ladicle in L. Exocarpi. I have also observed and depicted the same phenomenon 

 in the following species: L. congener Sieb., L. Miquelii Lehm., L. miraculosus 

 Miq. and the variety (b). L. No. 15, n.sp., L. Gaudichaudi DC, L. No. 24, n.sp., 

 L. vitellinus F. v. M. 



In the ma,iority of eases the development of the double radicle is unequal, 

 and a large percentage of them fail to develop into plants. As the two radicles 

 appear to exhaust the store of food witliin the endosperm before the suctoral 

 disc becomes established, it is evident that the double radicles are not always a 

 beneficent factor in the reproduction of the species, but, on the contrary, they 

 are detrimental to it. They are also subject to self-parasitism, which results in 

 the death of the one preyed upon, and occasionally l)oth succumb. 



It has been pointed out by many authorities that the Loraiith does not live 

 entirely upon the host. The presence of chlorophyll in the leaves and young 

 "branches is suggestive of the power of assimilation it possesses, and therefore 



