332 PHILOSOPHICAL XOTES OX 



The lobes of the Vitis disk being alternate with the stamens, 

 it is quite clear that they are suppressed stamens. In the rhodo- 

 dendron I have counted ten projections on the disk, and it became 

 quite clear to me that, corresponding with the ten stamens, they 

 also were suppressed male organs. 



Yet Prof. Henslow ("Floral Structure "), p. 4, says, in writing 

 of disks, honey glands, &c., " but as these, when they occur on 

 the floral receptacle, are merely cellular protuberances, and form 

 no part of the floral whorls proper — not being foliar in their origin 

 — they may be omitted, especially as their position is by no means 

 constantly the same in all flowers." In a note he somewhat 

 modifies the foregoing statement thus : " I do not here allude to 

 certain glandular structures, which may be the homologues of 

 arrested organs." 



The disk in my opinion is to stamens, and other floral divisionns, 

 what the stipule is to a leaflet, viz., an abolition of a part which 

 in allied flowers was developed. The disk is simply a return to 

 the cellular nipple (or amalgamation of nipples) from which all 

 foliar organs originated. 



It is no wonder, therefore, that the disk is cellular in structure, 

 as Prof. Henslow describes it. 



When a number of nipples fuse round an axis, they naturally 

 take the form of a disk. Similar fusions may, however, occur in 

 the abortive teeth of a leaflet, but then, not being disposed round an 

 axis, we do not call them disks, but glands. I refer to the fusion 

 of teeth-glands on the petiole of the cherry leaf (Fig. 85). In 

 both cases the nipples are abortions of reproductive organs. The 

 disk is an abortion of stamens, and the petiole-gland is an abortion 

 of a leaflet, the only parts that remain being the iQQth-glands, 

 amalgamated into a petiole-gland. 



Any whorl of a flower can become a disk whicli possesses 

 great elasticity, that is, it can contract into a whorl of nipples or 

 teeth, and under other circumstances, it can expand into a cup, or 

 split up into foliaceous organs. 



For instance, in Narcissus dejiciens^* we have the crown 

 reduced to teeth (snepe dentibus sex minutis coronas loco). Then 



* " Bot. Keg./' V. 33, p. 2. 



