154 Derby — Crown Structure of Ps<fronius Broziliensis. 



originating from the curved inner ends of the branches appear 

 at the base of this segment (to the right and left of C3), but 

 they did not persist to the higher level and thus are lacking 

 at the back of the figure. 



The younger F organs (Fl', F2') have here fully developed 

 their middle age characters, which must have appeared in the 

 comparatively short interval of growth between the highest 

 level attained by the oblique cut of fig. II and that of the 

 upper face of the Rio slice where their detached youthful ele- 

 ments appear united (presumably including, as already sug- 

 gested, sprouts originating from the inner face of the neigh- 

 boring P organs) and with sclerotized layers formed on their 

 outer face. They are here in essentially the same stage of 

 development as that shown in tig. 1 for the older pair whose 

 adult characters begin to appear in fig. II. 



In the C group of organs the detached parts of CI and C2 

 had ceased to grow before the level of the upper face of the 

 Rio slice was reached. Up to this level the succeeding pair 

 (C3, C4) showed no important modifications, but from here on 

 its members increased greatly in width and assumed the form 

 shown by C4 in the figure, and a succeeding pair (CI', C2') 

 began to be differentiated amongst the irregularly placed cen- 

 tral members of the group, preparatory to giving birth to a 

 new pair of F organs. 



If, barring some details, the above interpretation and resto- 

 ration of the preserved portions of the crown be accepted as 

 substantially correct, they afford a safe starting point for more 

 or less plausible conjectures regarding the un preserved por- 

 tions. While looking about among the plants growing around 

 me for analogies to guide such conjectures, a decapitated 

 female example of Cycas circinalis came under observation, 

 that afforded an opportunity for watching the development of 

 a new crown from the low vegetative cone exposed on the 

 truncated top of an apparently lifeless stump. 



At the beginning of its growing season the cone rose rapidly 

 upward for a few inches until it assumed the form of the top 

 of a small conical cabbage head. It was then seen to consist 

 of a closely compacted mass of flattened finger-like scale 

 leaves. From the apex of this cone the tip of the dower cone 

 appeared and soon developed into a larger pineapple-like sec- 

 ond cone superimposed on the first one. Later on, a few 

 lance-like frond sprouts shot upward with extreme rapidity 

 from the apex of the second cone, forming an extremely elon- 

 gated third cone. The base of the whole crown complex then 

 widened in such a way as to transform the three successive 

 cones into concentric rings of detached sprouts, which, as they 

 developed, commenced to spread outward at the top and even- 



