﻿98 VEGETATIVE FEATURES. 



CYCADEOIDEA COLOSSALIS (TRUNK 133). 



The general foliar form and relations just described in Cycadcoidea ingens are 

 repeated in fully as complete and clear detail in several of the Yale specimens 

 referred to Cycadeoidea colossalis, a quite different trunk type from either of the 

 preceding. Of these, Yale specimen No. 133 is noteworthy. This trunk not only 

 bears a lateral bud with very small fronds, the minute pinnules of which, with their 

 bundle systems, are indicated, but, succeeding the old leaf bases in regular sequence, 

 a fine crown of nineteen helicoidally disposed young fronds. Interior and apical 

 to these are some fifty segregated ramental areas representing yet younger leaves 

 and completing the usual apical helicoid foliar arrangement. The older of the 

 fronds of the young leafy crown were well advanced in growth, and in life pro- 

 jected beyond the ramentum, although here as elsewhere most projecting portions 

 of young fronds have failed of preservation or the tips have been broken or eroded 

 away. The more and more apical of the fronds — that is, the successively younger 

 members of the series — are less and less advanced in growth, and at last fail to 

 emerge from the enveloping ramentum. In the absence of sections it can only 

 be said of the larger fronds that they bore rather fewer pinnules than in C. ingens, 

 and that the pinnules are of linear acuminate outline, and 5 or more centimeters 

 in length, the breadth being less than half a centimeter. 



Further characters of these silicified leafy crowns are, however, remarkably well 

 shown in thin sections made from a stray bud, evidently from the crown of a truuk 

 of this same species, or, if not, from one of C. minnekahtensis. This specimen 

 (No. 520 of the Yale collection) is from the same locality as the preceding, and is 

 of the same general form, appearance, and type of preservation, being simply an 

 isolated crown of young leaves broken away from their insertion at the apex of a 

 trunk, above the old leaf bases, and on the line of the cortex. A careful drawing 

 of a transverse section, conveniently cut 5.5 cm. beneath the summit, is shown in 

 figure 52. At the periphery of the section a single one of the old leaf bases is 

 seen to have remained attached to the bud as broken away. Then follows a series 

 of sixteen young and yet folded fronds disposed in two nearly complete circum- 

 volutions of the frond helicoids, the section doubtless passing above the tips of 

 several still younger fronds in sequence with and of the same season as the 

 sixteen. Interiorly — and therefore apically to the fronds, which actually appear at 

 the surface — there is, however, an additional series of ramentum areas disposed 

 in the same continuously helicoidal system as the larger fronds, and in turn followed 

 by a circular zone of clear silica 5 mm. wide, which incloses centrally a somewhat 

 asteriated area of ramentum. This on closer inspection appears to belong to nine 

 deeply seated incipient fronds, inserted close around the true apex of the trunk. 



Since in the various transverse sections of the fronds only from eleven to 

 eighteen pairs of pinnules are cut, though some of the sections pass through the 

 rachides, the fronds of the present species have only about half as many pinnules as 

 those of C. ingens. It must be noted that scale leaves are not believed to be here 

 present. All the leaf axes appear to be very young or else actually bear well- 

 preserved pinnules. 



