ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 263 



these open into the three loculi immediately above the point of inser- 

 tion of the ovules, so that the pollen-tube is conducted straight to the 

 funiculus, which is swollen on the upper side, and densely clothed 

 with papillae, which project like a tuft above the micropyle. These, 

 like the papillae of the stigma, contain a red pigment. In Euphorbia 

 helioscopia the papillfe are densely filled with protoplasm, and tempo- 

 rarily with large starch- grains. The nucellus projects into the 

 micropyle, and is in immediate contact with these papillae. Similar 

 arrangements occur in Mercurialis annua, Linum usitatissimum, and 

 Citrus aurantium. In Phytolacca the funiculus is surrounded by a 

 crest of papillae, which reach the mouth of the micropyle. 



4. In Mahonia aquifolium the unilocular ovary contains four or 

 five basal anatropous ovules. Both the stigma and the stylar canal are 

 clothed with papillae. Only the upper part of the placenta is provided 

 with papillae ; in the lower part they pass into small cells, dis- 

 tinguished by their metaplasmic contents, and cuticularized. The 

 micropyle is at some distance from the placenta, and the further con- 

 duction of the pollen-tube is undertaken by the funiculus, the 

 epidermal cells of which are of a similar nature to those of the 

 placenta. A similar structure occurs in Liliacese {Ornithogalum nutans 

 and pyramidale, and Anthericum Liliago) with their trilocular ovary, 

 each loculus containing several ovules. In Verhascum Thapsus the very 

 conspicuous mucilaginous layer overlays both placentte, and the some- 

 what thickened funiculi. In Nuphar luteum the whole inner surface 

 of the ovary is covered with a granular mucilage. In the Cactace^e 

 the very long coiled funiculus is covered over its entire ventral 

 surface with long papillee. In Cruciferte (Lepidium virginicum and 

 sativum and Iberis amara^ we find similar contrivances. 



5. In Aroidete the ovules are usually orthotropous, but the posi- 

 tion of the micropyle often appears very unfavourable to the entrance 

 of the pollen-tube ; but in Atherurus ternatus the arrangement is much 

 more simple, and resembles that in Polygonum. In Arum maculatum 

 the single parietal placenta bears four or six orthotropous ovules. A 

 short canal extends from the style into the cavity of the ovary, 

 round the mouth of which, as well as covering the placenta, are uni- 

 cellular or multicellular papillae of various length. From these is 

 developed a mucilage which, at the time of blossoming, surrounds the 

 mouth of the canal and the ovules, reaching to the micropyle. lu 

 Philodendron pinnatifidum a similar structure is found. Acorus 

 Calamus is distinguished by the upper margin of the integument, near 

 the micropyle, being also developed into a long papilla. 



6. The least favourable structure for the conduction of the pollen- 

 tubes is presented by the free central placentation. In Calla 

 palustris the mouth of the stylar canal and each ovule is completely 

 surrounded by a tuft of papillae, between which is a large drop of 

 mucilage ; and a similar structure occurs in Luzula pilosa. In 

 Caryophyllacefe (Saponai'ia ocymoides and Lychnis vcsper(ina) are four 

 rows of campylotropous ovules, the micropyles in each pair of I'ows 

 always facing one another. Between these rows are two conducting 

 bands, which bear mucilaginous papillae. In Primulacefe [Anagallis 



