THE ANATOMY AND AFFINITY OF PLATYZOMA MICROPHYLLUM. 637 



which varies in detail from pinna to pinna. Irregularities in the numbers of the 

 lateral branches of the sympodium, and the tendency to establish sympodial 

 dichotomies, are the features worthy of note (text-figs. 1 to 5). The filiform 

 leaves varied much in both length and form. The longest measured some 2\ inches, 

 while the smallest were minute and slender structures of about ^ inch in length. 

 The larger filiform leaves were inserted chiefly upon the sides of the rhizome ; the 

 smallest sprang, almost invariably, from the lower surface. In fig. 7 a filiform leaf, 

 which measured about 1^ inch, is represented as seen from its lower surface. Three 

 distinct regions — a basal, middle, and terminal region — are recognisable. The basal 

 region measures about -g- inch. Its superficial tissues are dark brown and sclerotic, 

 and on its upper surface it widens out on both sides into a distinct flange. Beneath 

 each of these flanges is a shallow lateral groove. The flanges die out as the middle 

 region of the leaf is approached, but the grooves persist, and, having passed to the 

 lower surface, they deepen and run parallel until the terminal region is reached. 

 The middle region constitutes the greater part of the leaf, and variations in its 

 length are mainly responsible for variations in the length of the larger filiform 

 leaves. It is a more slender and delicate region than the leaf-base. Its superficial 

 tissues are not sclerotic, but its epidermis is strongly cuticularised. As has been 

 indicated, it is deeply grooved on both sides of its lower surface. On its upper 

 surface are found a pair of grooves, similar to those already noted on the lower 

 surface. These upper-surface grooves likewise continue to the terminal portion of 

 the leaf. The terminal region is short and bulbous. In it, both the upper and 

 lower pairs of grooves become rapidly shallow, and finally die out just before the 

 leaf-tip is reached. 



A leaf of the smaller type taken from the lower surface of the rhizome, and which 

 had remained almost hidden among the hairs, is represented in fig. 3. It measured 

 about J inch, and its tip was distinctly circinate. But in this case no division into 

 basal, middle, and terminal regions could be made, and no distinct grooves were 

 recognised. The leaf became gradually slender, and the superficial tissues passed 

 gently from a sclerotic to a strongly cuticularised condition, as one passed forward. 

 The great majority of the filiform leaves were of the first type, and only a very few 

 resembled the second type described. 



Four remarkable leaves formed a reduction series, illustrating a transition from 

 the typically pinnate to a filiform condition. The first stage in this reduction is 

 shown in fig. 5, which illustrates a leaf found among the broken petioles of dis- 

 carded leaves. It measured about l| inch in length, and possessed about 20 pinnae of 

 very variable size and irregular distribution. The lower third was entirely devoid of 

 pinnae, and might therefore be considered petiole. The remainder of the leaf was 

 mainly pinnate, and was therefore undoubtedly rachis. Here, then, as in the typical 

 pinnate leaf, the rachis bulked more largely than the petiole. The superficial tissues 

 of both petiole and rachis were sclerotic, as in the typical pinnate leaf, and neither 



