516 PART III.— THE CLASSIFICATION OF PLANTS. 



Some flowers are probably primarily moiiosporangiate (p. 505) ; 

 that is, there is no reason to believe that the monosporangiate 

 condition is due to the suppression of either micro- or macro- 

 sporangia {e.g. Hemp, Oak, Walnnt, Poplar, Willow). Others are 

 secondarily monosporangiate ; that is, there is reason to believe, 

 either from their development and structure, or from their relation 

 to allied ambisporangiate forms, that they are typically ambi- 

 sporangiate, but have become monosporangiate by suppression : 

 thus, in the Cucurbitaceae some genera (e.g. Cucurbita, Cacumis, 

 Bryonia, etc.) have monosporangiate flowers, whilst in others (e.g. 

 Schizopepon) the flowers are always ambisporangiate ; similarly, 

 in the Caryophyllaceae, the flowers are generally ambisporangiate, 

 but in the species Lychnis vespertina and L. diurna they are mono- 

 sporangiate ; and again in the Polygonaceoe certain species of 

 Rumex {^R. Acetosa, Acetosella, etc.) alone are monosporangiate : 

 in some monosporangiate flowers traces of the missing organs are 

 to be found, such as staminodia in carpellary flowers (e.g. Cocculus 

 and other Menispermaceae, Feuillea among the Cucurbitaceae ; 

 Laurus nohilis), or rudimentary pistils in starainate flowers {e.g. 

 Bhamnus cathartica, Cocculus, Lychnis vespertina and diurna). 



It sometimes happens that typically dioecious plants become 

 exceptionally monoecious (e.g. development of ? flowers on (^ 

 plants of Myrica Gale and Cannabis sativa ; or of ^^ flowers on $ 

 plants of Cannabis sativa and Mercurialis annua) : or that a typi- 

 cally diclinous monoecious plant bears some monoclinous flowers 

 (e.g. Ricinus). 



The Aridroecium comprises the microsporophylls (one or more) 

 of the flower, the stamens. Each stamen usually consists of two 

 parts ; a slender stalk called the filament (Fig. 331 s), and a 

 placental portion which bears the pollen-sacs (Fig. 331 Dp), known 

 as the anther (Fig. 331 a). The anther consists of two longi- 

 tudinal halves, termed thecoi, each of which__usually contains two 

 pollen-sacs ; these two halves are unitea by the placental portion 

 of the filament which is known as the connective (Fig. 331 c). 

 This is occasionally very narrow, so that the two halves of the 

 anther lie close together (Fig. 331 A^ a) : in this case it may be 

 that the anther is not sharply marked oft' from the filament, and 

 is attached throughout its whole length to the filament (adnate, 

 Fig. 332 C) : when the anther is sharply marked off from the 

 filament, it may be attached to the filament by its base, when it is 

 said to be innate or basifixed (e.g. Tulip) ; or the filament is in- 



