546 Mr. Hassall on the Structure of the Pollen Granule 



same plane and one resting upon these ; each granule emits a single 

 pollen tube. PI. XIII. fig. 8. 



Juncus articulatus. 



Obs. — The plants examined in the following orders of the groups 

 Hijpogynosa and Epigynoscc, commencing with the Butomacea and 

 going up to Musacetc, are with two exceptions characterized by the 

 possession of a pollen grain of the same form and structure as indi- 

 cated below. The first exception occurs in Limnocharis Humboldtii, 

 and is very remarkable, inasmuch as its pollen granule presents a 

 more complicated structure than that of any other endogenous plant 

 hitherto met with, while the second is seen in Anigozanthus coccineus. 



Char. — Granules of an elongated form, tapering towards either 

 extremity, sometimes slightly curved, each having on one side down 

 its long axis a fissure through which the pollen tube quits the ex- 

 tine ; this fissure is sometimes covered by an oval piece of membrane 

 which curls up and falls off the extine when placed in water; extine 

 either plain or reticulated. The whole granule may be very aptly 

 compared to a grain of wheat while it remains dry ; but as soon as 

 it is immersed in fluid, and before the emission of the pollen tube, it 

 becomes nearly circular. Extine often reticulated, and presenting a 

 very beautiful appearance under the microscope. See fig. 10 and the 

 following ones up to fig. 26. 



BuTOMACEjE. 



Butomus umbellatus. 

 1st Exception. 



Pollen grain of Limnocharis Humboldtii circular ; extine reticulated, 

 perforated with six or seven apertures for the escape of pollen tubes. 

 See fig. 9. 



CoMMELINACEJS. 



Pollen grain somewhat curved. See fig. 10. 



Tradescantia virginica. Tradescantia discolor. 



Liliacejs. PL XIII. fig. 11, 12. 



Haworthia radula. Arthropodium cirrhatum. 



Aloe obscura. Hyacinthus orientalis. 



A. saponaria. Bessera elegans. 



Yucca filamentosa. Eucomis striata. 



Asparagus officinalis. Albuca minor. 



Peliosanthes Teta. Ornithogalum speciosum. 



Convallaria majalis. Allium fragrans. 



Czackia Liliastrum. Scilla maritima. 



Pollen granules of most of the following genera reticulated, and 

 furnished with an oval appendage ; (two of the genera enumerated 

 above, Yucca filamentosa and Czackia Liliastrum, have their pollen 

 grains provided with a similar appendage). See fig. 13, 14, 15. 



Polianthes tuberosa. Tulipa Gesneriana. 



Agapanthus umbellatus. Lilium longiflorum. 



Funkia Sieboldiana. L. album. 



Hemerocallis flava. L. tigrinum. 



