86 PART I. THE MORPHOLOGY OF PLANTS. [ 17. 



specially adapted to bear the reproductive organs, in the one case 

 sexual, in the other, asexual. And just as an axis of the sporo- 

 phore bearing one or more sporangia (whether directly or on spon- 

 phylls) is termed a flower, and the sporophore itself an inflorescence ; 

 so these terms may be applied to the gametophore, though the 

 physiological differences between the sporangia and gametangia 

 must be borne in mind. It has, in fact, long been customary with 

 reference to Mosses, to speak of the sori of sexual organs, with 

 their perichaetia, as " flowers." 



(d.) The distribution of the Sexual Organs. The male and female 

 organs are either borne by the same gametophyte, or they are 

 borne by distinct male or female gametophytes ; in the former 

 case the organism is said to be monoecious, in the latter dinecious. 



The following are instances of monoecious gametophytes : 



Algce ; Volvoac Globator, Khynconema (Zygnemeae), Vaucheria, Sphseroplea, 



Coleoehaete, some species of Chara and Nitella, Fucus platycarpus, Hali- 



drys, Cystoseira, Pycnophycus. 

 Fungi ; monoecism is the rule. 

 Muscinete ; essentially monoecious. 



Pteridophyta ; homosporous forms generally monoecious, except Equisetum. 

 The following are instances of dioecious gametophytes : 

 Alga; Volvox minor, Eudorina, Conjugatae generally, Cutleria, most species 



of Fucus, Ozothallia (Ascophyllum), most Eed Algae. 

 Pteridophyta; Equisetum, and all heterosporous forms (Hydropterideae 



Isoeteae, Selaginelleae). 



The Phanerogams have not been included in the preceding list, 

 for the conditions which obtain among them in this respect are 

 peculiar, and demand separate consideration. Inasmuch as the 

 Phanerogams are heterosporous, they are essentially dioecious, since 

 each kind of spore produces its corresponding male or female 

 gametophyte. Bat in consequence of the fact (see p. 74) that the 

 macrospore is not set free, but remains attached to the sporophyte, 

 and germinates in that position, the female gametophyte is 

 attached to the sporophyte. On this account, and on account of 

 the rudimentary development of the male gametophyte (pollen- 

 tube), the spores, that is the pollen- grain and the embryo-sac, 

 have come to be inaccurately regarded as sexual reproductive cells, 

 and the stamens and carpels, which are really sporophylls, as 

 sexual reproductive organs. Hence a Phanerogam is said to be 

 monoecious when the same individual bears both stamens and 

 carpels, dioecious when they are borne by distinct individuals. 



