Gnetum , with some Notes on the Structure of Inflorescence . 615 
Until more complete information as to the structure of the axis of the 
spike in other species and in earlier stages of development is available, it 
is useless to seek for an explanation of the remarkable differences now 
shown to exist between G. scandens and some of its allies on the one 
hand, and the African species on the other. It is, however, worthy of 
emphasis that the most remarkable fact established in this investigation — 
viz. the presence of a series of strands descending to the nodal flower- 
complex — is associated with elongated internodes. It would be of great 
interest to know whether this association is constant. The structural 
differences found between the male and the female axes of the same species 
are such as might be anticipated in view of the much longer duration of the 
female spike and the greater demands made upon its vascular system. 
Speaking generally, these are (1) a tendency to lignification of the medullary 
tissues of the female and to mucilaginous degeneration of the same tissues 
in the male ; (2) the appearance of adventitious bundles ‘ augmenting ’ the 
inner series, and of transfusion tracheides associated with the cupular traces 
in the female and their absence from the male. 
The similarity of structure of the male spikes of the two African species, 
and the differences which separate them from those of the Indo-Malayan 
species whose anatomy is known, are of phylogenetic interest. If the internal 
characters of the female spike of G. Buchholzianum bear a close resemblance 
to those of G> africanum , as may be expected, the near affinity of these two 
will be more firmly established. But while nothing is known of the internal 
structure of the vegetative and reproductive organs of any of the eleven 
American species, nor of the majority of those which occur in the Indo- 
Malayan region, no definite conclusions can be drawn as to the phylogenetic 
position of the African species with regard to the rest of the genus. 
The hairs which occur among the flowers are usually of the character 
which has been described by previous writers. Occasionally, however, they 
assume the form of cell-plates, which are of interest owing to their 
resemblance to ramenta (Fig. 4). In the younger inflorescences the cells 
of the hairs contain starch. 
In the youngest flowers available the anther wall consists of an 
epidermis and two layers of tapetum (Fig. 5) ; these latter are clearly 
derived by tangential divisions from an initial layer. 1 As development pro- 
ceeds the outer of these becomes exhausted and flattened, while the cells of 
the inner undergo considerable enlargement (Fig. 6), and at length many 
of them become binucleate (Fig. 9). These stages are closely matched both 
in Ephedra 2 and in Welwilsc/iia . 3 By the time that the pollen-grains have 
reached the 3-nucleate condition, the outer tapetal cells are hardly re- 
cognizable, and those of the inner layer have preserved nothing of their 
1 Karsten (’93), Taf. viii, Fig. 14. 2 Land (’04), Figs. 5-7, 14. 
3 Pearson (’06), Fig. 4 ; (’09), Fig. 2. 
S S 2 
