6 INTRODUCTORY ESSAY. 
Sometimes the spines are confluent and, by their united bases, form membranous 
crests which are crowned by permanent or deciduous needle-like spiculae. 
Not infrequently the spines, especially when rather strong, leave on the surface 
of the sheaths or even on the underside of the leaf-rachis, a more or less distinct 
and deep impression of their outline; this is due to the fact that when the leaves 
are closely packed in the terminal shoot the spines are turned upwards, and are 
pressed against the surface of the organ from which they originate, while, after the 
expansion of the leaves, these spines become at first spreading and at length hori- 
zontal or deflexed. 
Whenever the rachis is prolonged beyond the ultimate leaflets as a filiform or 
whip-like appendix, or when a similar appendage crowns the summit of the spadix, 
or when leaf-sheath flagella are present, the armature of these parts consists of 
hooked prickles or claws, while at the same time the lower surface of the leuf-rachis 
and the attenuated portions of the spadices interposed between two partial inflor- 
escences are usually similarly armed. 
The claws at times are slender but more frequently they are robust, with 
a broad and swollen base and a very sharp and short curved point. In the first or 
lower portion of the rachis they are usually solitary, but they became 2-3-nate and 
even digitately 5-nate upwards when the rachis is prolonged into a cirrus; in this 
ease the claws usually form ł-whorls at regular intervals. In very robust species 
they even form {-whorls, the claws being then 6-7 in number and confluent by 
their bases. It is, however, very rare, except at the extreme apex, for the circle 
of claws to be closed and form a complete whorl. The leaf-sheath flagella and 
prolongations of the spadices, when present, are similarly armed. . 
The different kinds of spines of Calamus are all, as already stated, outgrowths 
of the peripheral tissues and consist of their lengthened cells with tapering ends 
(clostres), which are very closely united and form externally a very resistent sheath 
of prosenchyma, while the interior is composed of a more or less abundant wall-like 
or muriform parenchyma. In the spines of ©, Flagellum var. karinensis I have 
happened to find besides a few slender bundles of spiral vessels. 
Every kind of spinosity, but in an especial manner that of Calamus, is assumed 
by me to owe its origin to certain stimulative causes acting on tissues liable to 
hypertrophic cellular growth, I suppose therefore that a bite, a sting, even simple 
contact, or any other agency capable of irritating the !protoplasm, when in the 
full force of its vitality, may have produced, during the plasmatical era—that is to 
say, in the very early periods of the evolution of organisms, and under special 
eireumstances—certain local hypertrophic excrescences. These, having in the course of 
time acquired the power of being transmitted to the progeny, may have been 
changed into spines, | 
In the category of spines, rather than in that of rudimentary leaf-blades, I 
would also include the scales of the loricated fruits of the Lepidocaryee, 
III.—The Stem. 
The stem of Calamus is usually slender and very long; for as Calami are Palms 
of very rapid growth, the annular thickenings or rings of the stem where the leaves 
