81 



Isolation and separation continuing, we have the simple umbel 

 (Fig. 11) arising from the capitulum by the development of foot stalks 

 to the flowers. This natural advance suggested itself to my mind before I 

 was aware that it had been previously noticed. Compound umbels, from 

 ramification of the peduncles of their simple umbels, seem to follow as 

 a matter of course, and have been so set down. However, I am not 

 convinced that the peduncles ramify into pedicels, and produce invoht- 

 eels occasionally. The true course of development is otherwise. If an 

 umbel come from a capitulum, and that from a concave caenanthium, 

 whose antetype is a conceptacle, we must return back for a clue and an 

 illustration. Take an inflorescence, such as Tig. 4, and say that 

 here there are five conceptacles. Each of these five cavities, being 

 turned inside out, so as to form conical heads 'as shown with regard to 

 the Tig), we shall have five capitula. Let them have a peduncle deve- 

 loped to each, and we shall have an inflorescence, such as that seen in 

 Tig. 12, Matricaria camomiUa — a loose corymb, bearing composite flow- 

 ers. If those peduncles should arise at one point, and the sessile flowers of 

 the capitula get stalked, we should have a compound umbel of five prin- 

 cipal radiating peduncles. The involucres of the composite capitula 

 become the involncels of the umbellules, and the leaves in whose axils 

 these peduncles arise cluster together to form the general involucre. 



Supposing the axis of the composite flower to be prolonged, the 

 spike (Tig. 13) might be the result, as has been stated. It might even 

 have been added that the scales found often between the florets become 

 bracts. Bat what of the involucre '? Until the absence of anything to 

 represent it be explained, I shall believe it more natural to deduce the 

 spike as well as the spadix from the simpler forms ; as, for instance, 

 through the cone the abortive leaves, in whose axils (Tig. o) the pe- 

 duncles arise, becoming bracts in the spike ; then, as the axis was men- 

 tioned as prolonged into a tuft of leaves beyond the male cone oiPinus 

 syhestris, so in Tig. 14 we have the axis prolonged beyond the flower 

 head, leaving it as a glomerulus. This is a cymose circle of definite in- 

 florescence. 



What form anterior to, and yet foreshadowing the cyme of definite 

 infloresence, is to be observed ? At the extremity of the axis here the 

 reproductive organs are produced, and the plant becomes forked, eon- 

 tinning to develope by axillary growth. "Now, this is precisely what we 

 have in Ceramium (Tig. 16), one of the Tloridese, or red seaweeds. 

 Their favellse terminate axial growth there, and are subtended by axil- 

 lary ramuli in the same way. Any one who compares Tigs. 15 ( Ceras- 

 tium) and 16, will at once obseiwe their essential identity. This is 

 additional proof from morphology that the favellse are reproductive 

 organs, whilst the tetraspores, immersed in the ramuli, should be re- 

 garded as analogous to bulbels. 



IV. 



This arrangement of affinities appears corroborated by the acknow- 

 ledged relationships of certain families to certain others ; and likewise 



E. I. A.PE0C. VOL. X. if 



