PROCEEDINGS OF SOCIETIES. 317 



petiolar connatiou with connation round the back of the leaf. In 

 ' Enghsh Botany ' I observe that the condition is fairly enough 

 rexDresented by the artist, but, as I have already indicated, the 

 morj)hological peculiarity does not seem to have impressed itself on 

 the botanical mind. Dr. Bayley Balfour remarked that a good 

 deal of confusion existed as to the application of the term " stipule," 

 and showed that in some cases it was applied to structures of very 

 different appearance, and perhaps even of varying morx^hological 

 significance. — "On the Inflorescence of Senehiera didyma,'" by Prof. 

 Alexander Dickson. When at Plymouth last August during the 

 meeting of the British Association, I took the opportunity of 

 examining Senehiera didijma, a weed which grows in great abundance 

 on road-sides and waste places about the town, and I was much struck 

 with a remarkable peculiarity in connection with its inflorescence. 

 The inflorescence is, like that of the mass of cruciferous jDlants, 

 racemose. The racemes are *' oppositifoliar," and at first sight the 

 arrangement seems to be analogous to that of the oppositifoliar 

 inflorescences of Vitis or of Alchemilla arvensis, where the mflo- 

 rescence is really termmal, but thrown to the side by preponderant 

 development of a "usurping shoot," the axillary bud of the last 

 leaf produced by the primary axis before ending in the inflorescence. 

 This view seems further supported by the fact that of all the foliage 

 leaves, that ox)posite the raceme is the only one apparently destitute 

 of an axillary bud, which on this supposition would be represented 

 by the "usurping shoot." If, however, the plant is more closely 

 examined, a very remarkable condition is disclosed — one, indeed, 

 which offers a morphological problem of considerable difficulty, and 

 which, probably, can be effectually solved only by developmental 

 study. The peculiarity consists in the constant occurrence of a 

 solitary flower springing somewhere from the internode below the 

 raceme either about liaK way down towards, or almost close to the 

 level of the leaf below. So far as my observations go, the solitary 

 flower is never quite as low as the level of the lower leaf. It might 

 be supposed that fi-om almost immediately above the second last 

 leaf of the main axis, the bases of the terminal raceme of the 

 "usurping shoot" and of the axillant leaf of the shoot had all 

 become fused together. Now, although cases are known on the 

 one hand, of adhesion between the base of a terminal flower and 

 that of the usurping axis (e.g., Helianthemum vuhjare ; Payer), and, 

 on the other hand, between the base of an axillant leaf and that of 

 the usurping shoot in its axil [e.g., Sedum sp.; Payer), we do not 

 know of connation of all three together. It is possible, but I think 

 improbaj^le. The view which, after careful consideration, occurs to 

 me as most fuUy satisfying the conditions of this remarkable case, 

 may be stated briefly in categorical form as foUows : — 1. The 

 racemose inflorescence is terminal and properly begins just above 

 the level of the second last leaf. It would thus include the afore- 

 said solitary flower. 2. The raceme after producing one ebracteate 

 flower, produces at its second node. a foliage leaf from whose axil 

 the "usm-ping shoot" springs. By such an exjilanation we can 

 dispense with any cumbrous adhesion hypothesis such as I have 



