98 



POLLEN. 



■& hundred times greater than those of the Alpine Forget-me-not (Myosotis al/pestris). 

 It appears also that in many flowers which remain open but a single day or night, 

 as, for instance, the Gourd and Melon, Portulaca, Morina, and the various species 

 of Mirabilis, the pollen-grains are especially big. In a single anther-cavity of 

 Mirabilis Jalapa there are, on the average, 32, and in one of Borago officinalis 

 •60,000 pollen-grains. 



In form pollen-grains are generally ellipsoidal (c/. figs. 217'^ and 217 1*), at 



Fig. 217. — Pollen-grains. 



^ Cobma seandens. 2 Morina Persica. * Cucurbiia Pepo, * Passifiora Kermesina. « Circcea alpina, « Convolvtdus sepium. 

 7 Cannabis sativa. 8 Pinus Pumiiio. » Mimulus moschatus. 10 Albucca minor (dry and moistened). " Dianikus 

 Carthusianorum. ^^ Corydalis lutea. ^^ Qentiana rhwtica. ^* Salvia glutinosa, 1-8x80-90; * 6, 7, 8, 10 x 120-150; 

 11, 12 Xl80; «, », 13, '» X 220-260. 



any rate in quite half of all flowering plants. More rarely are they spherical 

 {figs. 217^'^'*'^''). In the liliaceous Tritelia they are narrow and lancet-shaped, 

 and in Morina (fig. 217 ^) biscuit-shaped. In the Pine the pollen-grain possesses 

 two hemispherical bladders, and resembles an insect's head with two huge eyes 

 (fig. 217^). In Grucianella latifolia they are barrel-shaped, and in Brugmansia 

 arborea shortly cylindrical. Next to the ellipsoidal form, the angular or crystalline 

 is the commonest. Thus the pollen -grains of the Nasturtium (Tropceolum) are 

 S-sided prisms, those of the Pansy ( Viola tricolor) 4 or 5-sided, and those of Lady's 



