﻿VEGETATIVE FEATURES. 



such a minor poiut. Hence it can only be stated that at the time of its silicifica- 

 tion this frond was an almost completely emergent one, although its petiole was 

 scarcely half the mature thickness and as yet comparatively short. 



The foregoing sections furnish important testimony as to the size and appear- 

 ance of the mature fronds. First, as to the number of pinnules: In section 168 

 thirty-eight pairs of pinnules are cut, and this is the highest number seen in any of 



Fig. 49. 



1 . Diagram of a hypothetical leal, with reduced number of pinnules, showing positions of sections represented 



in 2 and 3. o, o\ Plane of transverse section, figure 2; also approximately marks base of longitudinal 

 section, figure 3, 



2. Cycadeoidea ingensWard (type); transverse section (No. 46) through upper portion of young leaf. X4. 



For relative position, see figure 1. a, Upper side of an inner pinnule cut near summit ; b, fibro-vascular 

 bundle of pinnule cut near base ; d, axis of growth of rachis. The arrows indicate approximately the base 

 line, o, / t figure 1. 



3. The same specimen; longitudinal section (No. 47) through summit of young leaf. \ 4. For relative 



position, see figure 1, also line indicated by arrows in figure 2. a, Summit of a pinnule near apex of leaf; 

 b. Upper side of pinnule ; c, base line of section indicated in figure 1 , o, o' '. 



4. The same specimen ; transverse section through a single pinnule, showing a fibro-vascular bundle. X60. 



a. Upper side of leaf ; b. hypodermis ; c, sclerenchyma connection of hypodermis with fibro-vascular bundle ; d, pali*ade 

 parenchyma ; e. xylem ; f, phloem : g, sclerenchyma and spongy parenchyma region ; h, epidermis of under side of leaf. 

 The centripetal xylem is marked by e. Beneath are several cells of centrifugal xylem, and to the nether side of the 

 bundle sheath on both sides outlying cells supposed to represent a transfusion tissue. 



