50 The Ottawa Naturalist. [June-July 



this displacement does not occur, the abscission rlane of the 

 peduncle is transverse through the 1:ase; if displacement has 

 intervened, the abscission plane runs down the false internode, 

 as it may be called, and, in extreme instances, as far as the node 

 below. It should be stated that the displacement in question is 

 ahvays greater on the upper side of the dorsiventral shoot in such 

 a manner as to cause a slight axial rotation of the peduncle. 

 We must, therefore, conclude that abscission in the cotton is 

 always through the base of the peduncle, and when it is decurrent 

 it is so because the base of the peduncle is stretched out in con- 

 sequence of the extension of the nodal zone. The position of 

 the plane of separation is marked by a low ridge. There is, 

 indeed, especially visible in flower buds and quite }-oun gbolls a 

 slight groove parallel and close to the base, but this has no con- 

 stant relation to abscission, contrary to Ball's statement. 

 The Abscission of Floral Parts. 



The separation of the parts of the flower may, on similar 

 grounds, be compared with that of the leaf. It occurs normally 

 toward the close of anthesis, and, indeed, may be taken as its 

 index, just as the unfolding of the flower-bud marks the begin- 

 ning of this critical period. The whole matter is too complex 

 and varied for brief presentation, so that it must suffice to make 

 a mere suminary. With the culmination of flowering, any of 

 the organs taken separate^, or any structural segregate of 

 them , may be found to fall away. The sepals (e.g., in Sangtiinaria 

 Impatiens, Cruciferae, etc.), petals, stamens, anthers or styles 

 may do so, or the corolla as a whole in the sympetalae, or the 

 corolla and androecium in one piece (Malvacecp) synchronoush^ 

 with, but independently of, the style, and so on. Conversely, 

 these parts may be variously adherent, and whither in situ, 

 affording another case of disharmony. Witness the frequent 

 adherence of the calyx (Rosaceae), of the androecium (Legumin- 

 osae) and even the corolla (e.g., many Orchids, etc.), specific 

 instances being afforded by the previously cited Cereiis Thnrheri 

 by Echinocacius Emoryi, and by Habenaria among the orchids. 



The position of the abscission plane, as in the leaf, is near 

 the base of the organ or complex of organs involved. Its 

 direction is, however, subject to more variation than it is in the 

 leaf, and may run much more obliquely. For example, this 

 direction in the corolla of the cotton flower varies from transverse 

 (which is rare) to an obliquity of 45 per cent., which is usual. 

 The style of this plant calls for special notice in this connection. 

 Separation of this organ begins during the second afternoon of 

 anthesis, and may usually be detected at about 3 o'clock. But 

 instead of being confined to one level, it occurs at several, so 



