MR. W. C. WILLIAMSON ON THE HISTORY OF ZAMIA GIGAS. 666 



The Stem. — The exterior exhibited numerous rhomboidal cicatrices Left by the fallen 

 fronds. The drawing (Plate LIII. fig. 6) represents a portion of the specimen referred 

 to. The canity was filled with brown pulverulent carbonaceous matt it, mixed with a 

 white aluminous substance (Scarbroite), these being the remains of the solid tissues of 

 the stems, from which all traces of minute structure had disappeared. The mrfa< is 

 divided by a network of elevated ridges into a number of irregular losengc-s] ipt <1 spnees, 

 markin * the existence, in the original bark, of deep clefts or fissures, separating the base 

 of each petiole from those of its neighbours. Within each area thus circumscribed is a 

 raised oval or diamond-shaped cicatrix, surrounded by a deep depression. This wa-, of 

 course, reversed in the original, and hence the cicatrix was really one with elevated 

 margins and a depressed centre. On the surface of each cicatrix the cast exhibit*, * itb 

 a considerable degree of uniformity, a deep longitudinal fissure, as well as some oblique 

 but less sharply defined ones towards the upper part. These represent corresponding 

 projections in the stem ; but whether they indicate the arrangement of the fibr. h ascular 

 bundles or irregularities resulting from accidental contraction, I am doubtful There 



5 UIlulul,JO j-v^v— ^ 



are also some other minor but less uniform rugosities on the surface of each 

 In the large example at Hawsker the scars were somewhat larger and farther aj 

 in the specimen figured; its diameter was uniform throughout, like the gene 



of Cycas circinalis or C. media. 

 In the collection of Mr. Ripley there is a specimen which is obviously the apex of 



al habit 



rith portions of seven or eight diverging fronds 

 traces of the cicatrices seen on the lower part of the stem 



As these fronds 



Its 



dition, also, has almost obliterated all superficial characters. It confirms, however, what 

 has been already said respecting the elongated contour of the original stem. 



Mr. Ripley's cabinet also contains a cylindrical specimen, 4 inches m length, and 

 having a diameter of U inch at one extremity and 1* at the other, which repr sents, 



I believe, the interior of the vascular cylinder. Its surface is marked with 

 interrupted longitudinal grooves and ridges, from half an inch to an inch long, formed 

 by the openings through which the vascular bundles passed to the — 



The Fi 



*> 



Sooner leaving the ^ te dO*ted la* ***££££ 



* i t l t«nrY\ it* origin °*ives on tlie small iuuh. i> 



from i to i inch, and at a short distance from its oiyn 



. in .est U Cycads ; these rapidly increase * len S t - ^J " 



mehes. Eaeh foliole is acuminate and sll S hl ^e™ds the greatest diamet r of 

 fixed somewhat obliquely upon the -VV^^^^' asl J „,, ail(1 h* 



«« leaflet is a little beyond its «fl. ^ £«£ ^tended with paren- 



either been planted upon an enlargement ot the lacms, ^^ ^.^ exhi , )its 



ehyma, as is common amongst living species of ^^^^ base; of these, 

 numerous slightly divergent nervures radiating no ^ ^ h ^ 



about two-thirds are distributed to the upper margm ofjach lea , 

 apex, and the remainder disappear along its inferioi mar n 



* In this 



- 



He 88YS. 



• a „ not i*rce with the Yorkshire ■? .mens. 

 * On this point Brongniart's description of Zamdes does n<* * B^ ^ ^ ^ ^ ^ y fMf _ ct ^ . 



amongst other characteristics, that they have, " nervures parables ^^ h;f „ rqui es lorsquc la foliole t rgic 

 quent convergent* vers le sommet ; fines et egales entre elles, 



tres-rarement fnj _ 



5 A 2 





