186 BOTANICAL GAZETTE | AUGUST 
the haustorium, in the enlarged sucker. Then the cotyledons and the remainder 
of the endosperm are cast off and the plumule appears. This small structure 
develops minute leaves in pairs upon successive nodes separated by very short 
internodes, the leaves falling soon after formation. Only after the haustorium 
has penetrated the host does any development of branches take place; then, 
however, growth becomes very rapid and large leaves form. Mr. Keeble 
interprets the growth of a lateral aerial root from the sucker, a phenomenon 
which not infrequently occurs before the penetration of the haustorium intothe 
host, especially on small or poorly nourished branches, as throwing light on : : 
the manner in which these plants became parasitic. ‘The seeds, originally 
sticky, often lodged on trees, and, as in many species of Ficus, these seeds, 
germinating, threw out roots which rapidly reached the ground, or the earth ae 
which collects in the forks of trees. To enable the plant to exist in this : : 
early non-parasitic stage, the base (free end) of the sucker came to functionas@ 
reserve food store. From this stage the natural semi-parasitism was reached 
by the ability of certain cells of the distal end of the hypocotyl to penetrate 
the host.”’ ; 
The curvature of the hypocotyl, above referred to, has long been known — 
to be independent of gravitation (it is ageotropic) and has been attributed - 
he influence of light (it is negatively I pic, and hence bendstowate 
the central shaded portion of the tree to reach the branch upon which the seed 
has fallen and stuck); but Keeble demonstrates, by germinating the seeds 
the dark, that the hypocotyls of some species imitate tendrils, and hence aes 
often do, succeed in applying their enlarged heads to the surface of branches! 
this way. Owing to the resinous matter which covers them, the heads stick. 
In these species, the nutation may cause the head or sucker end of the hype 
cotyl to point temporarily directly towards the light, but it obviously supple 
ments the negatively heliotropic curvature at other times and hence is rea 
tageous to the seedling. Though the general surface of the hypocotyl is 
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Srowth as is produced by contact with a suitable host. On the other 
to be induced by contact with any solid body. Keeble describes an exper" 
ment in which he applied a small cover-glass to the head of the hyper ee 
L. loniceroides, with the result that there was only slight enlargement ae 
head, which had not developed an effective sucker, though it remain¢ Bu 
by reason of the adhesive resin, whereas the haustorium had grows ee 
distance of 2™™ beyond the margin of the disc, being deflected from - ae 
by impenetrable glass. The cells which form the central part of the 
