426 PHA NER O GA MS. 



heneath the sexual organs on the same axis differ from the rest of the leaves of the plant 

 in their arrangement, form, colour, or structure, and are physiologically connected with 

 fertilisation and its results, they are considered as belonging to the flower, and are 

 termed collectively the Floral Leaves or Perianth. The separate flowers are dis- 

 tinguished from the Inflorescence by including, together with their sexual organs and 

 perianth, only one axis, while the inflorescence is an axial system with more than one 

 flower^. Roper has termed the tout ensemble of the male sexual organs of a flower the 

 Andrcecium, that of the female organs the Gynceceum. When a flower contains sexual 

 organs of both kinds it is called hermaphrodite or bisexual ; if it contains only male or only 

 female sexual organs, and is therefore unisexual, it is termed diclinous ; when flowers of 

 both sexes occur on the same individual plant, the species is moncecious, when on diff'erent 

 individuals it is dioecious. Usually the apical growth of the floral axis ceases as soon as the 

 sexual organs make their appearance, and frequently even earlier ; the apex of the floral 

 axis is then concealed, and is often deeply depressed in the centre of the flower ; but 

 in abnormal cases (and normally in Cycas) the apical gro\\i:h of the floral axis re- 

 commences, again produces leaves, and sometimes even a new flower ; and a Proliferous 

 Flocwer is thus produced. The sexual organs and perianth of a flower are usually 

 crowded (arranged in rosettes either spirally or in whorls) ; the part of the floral axis 

 which bears them remains very short, no internodes being in general distinguishable in it ; 

 and it not unfrequently expands into the form of a club or disc, or becomes hollovv', and 

 this part of the floral axis is called the Torus or Receptacle. In Coniferae and Gycadeae 

 (occasionally also in Angiosperms), it is however sometimes elongated to such an extent 

 that the sexual organs appear loosely arranged along an axis in the form of a spike. 

 Beneath the receptacle the axis is mostly elongated and more slender, either entirely 

 naked or bearing one or two small leaves or Bracteoles. This part of the axis is the Peduncle ; 

 if it is very short, the flower is said to be sessile. No shoots usually arise from the axils 

 of the floral leaves, even when they are produced in all the other leaf-axils of the plant ; 

 there occur, however, abnormal cases (which are not very uncommon) of axillary 

 branching or prolification even within the flower. 



The Male Sexual Cells {Pollen-grains), which are equivalent to the microspores of 

 the higher Cryptogams, arise in receptacles corresponding to the sporangia in those 

 plants, and may be termed in general Pollen-sacs. These are at first solid masses of tissue 

 in which, as in the sporangia, an inner mass of cells becomes differentiated into the 

 mother-cells of the pollen-grains (at first by more vigorous growth of the single cells), 

 while the surrounding layers of tissue become developed into the wall of the pollen-sac. 

 It has already been mentioned that the mother-cells of the pollen become separated and 

 detached from the tissue (though this rule is subject to exceptions), and then produce 

 the pollen-cells by division into four after actual bipartition or at least an indication of 

 it. A special description of these processes will be given under the heading of the 

 separate classes ; at present we must however premise a few facts relative to the 

 morphological nature of the pollen-sac. Like the sporangia of most Vascular Crypto- 

 gams, the pollen-sacs of Phanerogams are usually products of the leaves, which how- 

 ever mostly undergo in this case a striking metamorphosis, remaining much smaller 

 than all the other leaves. A leaf which bears pollen-sacs may be termed a Staminal 

 Leaf or Stamen ; the most recent researches have, however, shown cases in which the 

 pollen-sacs arise on the elongated floral axis itself, as Magnus has illustrated in the 

 case of Naias, Kaufmann in Casuarina, and Rohrbach in Typha ; in these cases it is 

 still doubtful whether the pollen-sacs may not be the only surviving portions of 



^ In some cases it is however difficult to distinguish between a flower and an inflorescence; 

 as in some Conifers, and especially in Euphorbia. (On the latter, see Warming in Flora 1870, 

 no. 25; Schmitz, ditto 1871, nos. 27, 28; and Hieronymus, Bot. Zeitg. 1872, no. 12.) [E. Warming, 

 El- Koppen lios Vortemcelkcn en Blomst eller en Blomsterstand, Kobenhavn 18 71.] 



