DISTRIBUTION OF SEXES. 297 



the genera Homogyne and Heliclirysum may be taken as typical, where the ray- 

 florets are not tongue-shaped but threadlike. This arrangement is rarely met with 

 except in these Composites. Strangely enough, it occurs in a species of Gladiolus 

 {Gladiolus segetum). 



The fifth group is made up of species where every plant bears both herma- 

 phrodite and true staminate flowers. For examples we have the so-called White 

 Hellebore ( VeratruTu), the Crown Imperial (Fritillaria imperialis), the Snake-root 

 {Calla palustris), and numerous Grasses belonging to the genera Andropogon, 

 Arrhenatherum, Hierochloa, Holcus, and Pollinia. 



A sixth group comprises those species in which every plant bears both 

 true pistillate and pseudo-hermaphrodite male flowers, but none that are truly 

 hermaphrodite. In this group are placed the Marigold (Calendula), the Colt's- 

 foot {Tiissilago), and Microjius. Here tubular staminate flowers (which are really 

 pseudo - hermaphrodite) occupy the centre of the capitulum, and true pistillate 

 flowers, either tongue-shaped or filiform, occur at the circumference. The Edel- 

 weiss (Gnajyhalium Leontopodium) and the Butter- bur (Petasites) also belong to 

 this group. In the two last-named plants, however, the arrangement in the single 

 capitula is of a peculiar kind differing from tliat in the other Composites mentioned. 

 There are three kinds of individuals of Edelweiss. In one the central head of the 

 whole inflorescence contains only pseudo-hermaphrodite male flowers, whilst in the 

 second form the central capitulum is again formed entirely of pseudo-hermaphrodite 

 male flowers, but in the other capitula these are surrounded by true pistillate 

 flowers. In the third form all the capitula have pseudo-hermaphrodite male 

 flowers surrounded by true pistillate flowers. In the Butter-bur (Petasites) all the 

 capitula have pseudo-hermaphrodite male flowers in the centre, and true pistillate 

 flowers around the circumference, but strangely enough the number of these varies 

 from plant to plant. In some plants the pseudo-hermaphrodite male flowers are 

 very numerous, and the capitula contain but few true pistillate flowers and vice 

 versa. These two kinds of plants differ very much in appearance, and the Butter- 

 bur might therefore be easily mistaken for a dioecious plant. 



The seventh group includes all those species in which each plant develops both 

 true staminate and true pistillate flowers, si^ecies which have been previousl}^ 

 termed monoecious. Examples of this large group are: Oak (Quercus; see fig. 

 286), Hazel (Corylus; see fig. 235, p. 147), Alder (Alnus; see fig. 228, p. 135), 

 Walnut (Juglans; see fig. 184, vol. i. p. 742), Pine (Pinus; see fig. 233, p. 144), 

 many Urticacese (Urtica urens, Pachysandra), -numerous Aroids (Arum, Ariopsis, 

 Arisema, Bichardia, &c.), many Palms, a number of marsh and water plants 

 (Alyriophyllum, Sagittaria, Sparganium, Typha, Zannichellia), some Grasses 

 (Heteropogon, Zea Mays), and, especially, many Euphorbiacece and Cucurbitacese. 



Species belonging to the eighth group have three kinds of flower .side by side 

 on the same plant, i.e. pseudo-hermaphrodite male and pseudo-hermaphrodite female 

 flowers and true hermaphrodite flowers. Examples are furnished by various Acers 

 (Acer Pseudo-platanus and platanoides), Sumachs (e.g. Rhus Cotinus and Toxi- 



