POLLEN. 



99 



igers (Anthyllis vulneraria) short 6-sided prisms with striated angles. A 

 bical form obtains in the pollen-grains of Triopteris brachypteris and Basella 

 ha, that of a pentagonal dodecahedron in Banisteria, Rivina, and, in particular, 



a number of Caryophyllaceas, e.g. Arenaria, Silene and Dianthus (cf. fig. 217"). 



the Dandelion {Taraxacum officinale), and in Corydalis lutea many crystalline 

 rms occur, side by side, in the same anther {cf. figs. 217^2 a^^j 2I8*). The 

 trahedron, also, is not infrequently met with. This form occurs in Thesiwm, 

 iphea, many Proteacese and Composites, sometimes with flat, sometimes with 

 rved surfaces {cf. fig. 218^). A form, made up as it were of two spherical 

 [angles joined together, occurs in Circcea and many other Onagraeese (fig. 217 ^). 



The above paragraph relates solely to the varieties in form of dry pollen-grains. 

 I the great majority of cases the grains are variously striated and grooved. In 

 iipsoidal and spherical grains, the grooves run like meridian-lines, so that two 



Fig. 218.— Pollen-graiM. 



'ympTuxa alba. 3 Viscum aibwm. « Ca/rlma acaulis. * Taraxacum o^cinale. * Cirsium nemorale. 

 grandifloruTti. ^ Hibiscus tamatus. ^ Malva rotuTidifolia. ^ Campanula persicifolm; x200. 



< BupTithalmum 



lies are distinguishable. The number of the grooves is constant for a given 

 ecies, and even for whole families of plants. A single furrow is characteristic 



the grains of the Tulip-tree, Magnolias, and Water Lilies (fig. 218^), of the 

 eadow Saffron, Tulip, Lily, Iris, Narcissus, and Snowdrop, of Palms, Grasses, and, 

 deed. Monocotyledons generally. Two furrows are found on the pollen-grains of 

 ilycanthus, several climbing Smilacinese {Tamus, Dioscorea), and several species 



Amaryllis. A very great number of plants have three grooves, e.g. Rock-roses, 

 olets. Poppies, Ranunculaceae, Roses, Almonds, many Papilionacess, Beeches, Oaks, 

 d Willows, Solanaceae, Gentians, Scrophulariacese, and many Composites 

 ^. figs. 217'* and 218*). Four grooves have been noticed in several Boraginese 

 .nchusa, Nonnea), some Labiates {Teucrium, montanum,, Sideritis scordioides), 



Houstonia, Platonia, Blackwellia and Cedrela odorata; six in most Labiates 

 g, 217 ^*), nine or ten in Sherardia, Borago, and Symphytum,; twelve in 

 •ucianella latifolia; sixteen in Polygala cham,OBbva;us ; twenty -one to twenty- 

 ree in Polygala rayrtifolia. On crystal-like pollen-grains the grooves are 

 tremely delicate, and their number depends on the number of angular ridges. 



