Structure. 87 



are composed of two distinct lamellae, which easily fall apart along their 

 smooth surfaces of contact. In all other species there is no such division 

 in the walls, but the tissues in each partition are perfectly continuous. 

 The first group was called on this account Lytopleura [Xuzo<; free, nhupd, 

 side), with the definition "carpella toto latere libera tantum externe ad 

 dorsum et interne ad processum axilem coniunctum enata." The remain- 

 ing group was called Symphytopleura (oufupuToz, connate), and defined "car- 

 pella toto latere coniunctum enata." It seems desirable, however, to get 

 rid of names as far as possible, so we have adopted the simple descriptive 

 terms "apocarpous" and "syncarpous" for the two groups. It is valuable 

 to keep in mind that apocarpy occurs in a large group of Nymphaeas, 

 as the Cabombeae and Nelumboneae are all apocarpous. The dehiscence 

 of the fruit of Nuphar, N. flava, and the fossil Ancectomeria into separate 

 carpels suggests a recent apocarpous ancestry.' 



The absence of any definite placenta in Nymphaea has long been a 

 subject of remark. The ovules are attached in large numbers all over the 

 walls of the ovary cells, both lateral and dorsal. They are anatropous, 

 and, at the time of flowering, are suspended on the funiculi with the micro- 

 pyle upward. The cells of the ovary are oval in side view, wedge-shaped 

 in transverse section, and are filled with a stiff, colorless mucilage. 



Externally the ovary (or receptacle) is densely covered with fibrous 

 and mucilaginous hairs. Those of the first type are few and early decidu- 

 ous in A^. zanzibariensis X , but plentiful in the other species examined ; 

 they are plainly visible in the Lotos group. The longest I noted in N. 

 odorata was 0.34 mm., and in N. 0. minor 0.66 mm., composed of two shaft- 

 cells ; the longest in N. tuberosa was 0.3 mm., with three shaft-cells ; in 

 N. zanzibariensis X 0.25 mm., five-sixths of its apical part being a single 

 cell. The epidermis is about 0.15 mm. thick, composed mostly of cubical 

 cells. Within this is a layer of dense tissue about 0.34 mm. thick, of small 

 polyhedral cells with very minute intercellular spaces, followed by a loose, 

 spongy tissue with very large air-spaces. In N. zanzibariensis X the air- 

 space in the latter zone barely exceeds the cellular tissue in volume and 

 there are no idioblasts. In N. tuberosa and odorata the air-space greatly 

 preponderates, and in the latter stellate cells abound. The spongy layer 

 is much narrower and idioblasts very scarce in N. odorata minor. The 

 epidermis bounding the ovary cells is backed by a single continuous layer 

 of soft parenchyma cells. In Syncarpiae this layer and the lacunar per- 

 enchyma are alone present between the epidermal layers in the partitions 

 of the ovary. In Apocarpiae the condition is very different. The line of 



