﻿FOLIAGE. 



8 9 



the sections from the present trunk. But the only means of determining how many 

 pairs in excess of 38 were commonly present would be to cut several fronds length- 

 wise a little to one side of the line of pinnule insertion ; and this has not been 

 done, partly because it was hoped that it might yet be more expedient to do so in 

 the case of some other specimen, and partly because, as is well known, the number 

 of pinnules may vary greatly in a given species of living cycads from year to year, 

 as well as in the leaves of the same year on the same plant. As the mass of pin- 

 nules is closely packed, however, and the rachis is about 5 cm. in length, it is likely 

 that not less than sixty, and possibly a hundred or more pairs of pinnules were borne 

 by each of the once-pinnate fronds, as here seen emerging in their normal position 

 at the summit of the trunk. 



As determining the general form of the pinnules, it is next to be noted that in 

 transverse sections like those shown in plate xix, photographs 1 and 2, the pinnules 



Fig. 49 — continued. 



5. The same specimen ; longitudinal section through a pinnule, cutting the palisade parenchyma just beneath the 



hypodermis. '■ 35. a. Forking vein ; b, palisade paienchyma. 



6. The same specimen ; transverse section through the ramentun surrounding the young leaves. X 60. 



next to the rachis are necessarily cut through or close above their insertion, while the 

 pinnules distal to the rachis — that is, at the inner side of the folded frond — are cut 

 near their tips. It follows that in these and similar sections (as may the better be 

 understood by reference to text-figure 49, 1, of the hypothetical frond) there is a 

 consecutive series of pinnules cut transversely at successively higher levels from 

 base to tip ; whence the transverse sections through the ranked pinnules of the folded 

 erectly prefoliate fronds here described virtually afford serial mounts of pinnule sec- 

 tions, such as would be obtained were one to cut serially from base to tip of a single 

 pinnule as many as 38 transverse sections, these being placed in close order one 

 after the other, and oriented alike. Again, each of these sections of silicified fronds, 

 cut low enough to strike the rachis, shows virtually the general form of the result that 

 would be obtained if a single pinnule from a living cycad frond were sectioned trans- 

 versely and serially from base to tip ^8 times, more or less, and the individual sections 

 mounted together in the exact order in which they were cut, as well as the most com- 



