POLLEN. 



POLLEN. 



d. Outer coat with irregular reticulations : 



Alstrccmeria Curtisiana. 

 Among the Orchideae are found quater- 

 nate grains belonging to this group. 



** Outer coat with two furrows : a rare 

 form, occurring in species of Ponte- 

 deria and Amaryllis, Tamus commu- 

 nis and elephantipes, Tigridia pavo- 

 nia, Calycanthus jftoridus, fyc. 



*** Outer coat with three longitudinal 

 furrows. 



a. Outer coat granular. One of the com- 

 monest forms: Quercus Robur, Viola 

 odorata (PI. 40. fig. 6). 



b. Outer coat with short spines : Cactus 

 flagellifonnis, Viscum album. 



c. Outer coat with cell-like reticulations : 

 Statice (PI. 40. fig. 29), various Cruci- 

 ferae. 



Outer coat with more than three 

 furrows. 



a. Four : very rare as normal, Houstonia 

 cceruka, Cedrela odorata] occasionally 

 occurring where three is the normal 

 number, as in Solanum tuberosum. 



b. Six : some of the Labiatae and Passi- 

 floreae (PI. 40. fig. 20), Ephedra dista- 

 chya, Heliotropium grandtflorum. 



c. A large number of furrows : many 

 Rubiaceae, e. g. Sherardia arvensis (PI. 

 40. fig. 18). 



The pollen of the Pines is related to this 

 group, also that of Nymphcea Lotus, Victo- 

 ria regia, and other plants, where the fur- 

 rows or thin places occupy the greater part 

 of the wall, and the outer coat forms only 

 segmental pieces. In Thuribergia alata 

 (PI. 40. fig. 24 a) a remarkable appearance 

 arises from the furrows running in a curved 

 or spiral direction. 



C. Outer coat with pores. 



* A single pore : Grasses, Sedges, Ty- 

 pha angustifolia, Sparganium ra- 

 mosum. 



** Two pores : Colchicum, and a few 

 other Monocotyledons; also Brous- 

 sonetia. 



*** Three pores. 



a. Outer coat granular : Dipsaceae, Urti- 

 cacese, Onagraceae [here the pores form 

 projecting processes (PI. 40. fig. 14) ; 



and in Morinda persica this is still more 

 the case] ; Cucumis sativus. 



b. Outer coat with cell-like reticulations : 

 many Passifloreae with large lids, P. 

 cceruka (PI. 40. fig. 13), alata, fyc. 

 #*** Four pores. 



a. Pores on the equator : Pistacia tere- 

 bintlius, Campanula rotundifolia, fyc. 



b. Pores not equatorial : Passiflora ker- 

 mesina, Impatiens Balsamina (PI. 40. 

 fig. 21) (Noli-me-tanyere). 



***** More than four pores, 

 t Distributed regularly. 



a. On the equator : Alnus glutinosa, Ul- 

 mus campestris, Collomia linearis, Cam- 

 panula Speculum. 



b. All over the grains : Basella alba (PL 

 40. fig. 19). 



ft Scattered irregularly. 



a. Outer coat slightly granular : many 

 Nyctagineae, Convolvulaceae, Chenopo- 

 diaceae, Alsineae, Alisma Plantayo (PI. 

 40. fig. 10), Plantago lanceolata, Riles 

 nigrum, Cactus Opuntia, fyc. 



b. Outer coat granular and spiny : Cucur- 

 Uta Pepo (with lids, PL 40. fig. >), 

 Malvaceae (fig. 26). 



c. Outer coat with cell-like reticulations : 

 Polygonum amphibium, pei'sicaria, Co- 

 bcea scandens. 



Compound porous forms occur in some 

 of the Onagraceae, and in Drimys Winteri, 

 where four grains are conjoined tetrahe- 

 drally. In the Mimoseae groups of eight 

 or sixteen (PL 40. fig. 25) occur in various 

 forms. In Leschenaultiaformosa the grains 

 are quaternate, lying in one plane. 



D. Outer coat with both furrows and pores. 



* Grains rounded or depressed, with 

 three depressions, each with a pore : 

 most Dipsaceae and Geraniaceae 

 (sometimes only two occur, PL 40. 

 fig- 22). 



** Three furrows and three pores. 



a. Outer coat granular : a very common 

 form among Dicotyledons. 



b. Outer coat spiny : most Compositae. 



c. Outer coat with cell-like reticulations ; 

 rare : Syringa vulgaris, Ligustrum vul- 

 gare, Grewia occidentalis, and other 

 species. 



