ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 351 



The nucleus of the ovum-cell divides shortly before fertilisation 

 without the formation of a ventral canal-cell. The upper part of the 

 ovum-cell, with its nucleus, becomes converted into mucilage, destroys 

 the neck-cells, and escapes from the archegone. The pollen-tubes have 

 two nuclei, in addition to those of the two generative cells. Each of 

 the generative cells has a nucleus entirely filled with metaplastic sub- 

 stance surrounded by a thin layer of dense protoplasm. After the 

 contents of the pollen-tube have passed into the ovum-cell, one of the 

 generative nuclei fuses with the ovum-nucleus ; the second generative 

 nucleus remains in the upper part of the archegone, undergoing later 

 amitotic division. The fertilised ovum-nucleus moves to the centre of 

 the ovum, where it divides karyokinetically three or four times. A 

 number of cells are formed in the lower end of the archegone from the 

 daughter-nuclei by free cell-formation. These cells are arranged in 

 stories ; from the lower story is formed the so-called rosette ; the next 

 one producing the suspensor-tube. Above this is a layer of cells from 

 which the embryo is produced. The morphological apex of the embryo 

 is formed of a single cell. 



Development of the Pollen in Convallaria and Potamogeton.*— 

 Mr. Karl M. Wiegand has followed out the development of the micro- 

 sporange and microspores in Convallaria majalis and Potamogeton folio- 

 sus. The archesporial cells arise from the division of a hypodermal cell 

 at one corner of the anther ; the archespore, therefore, does not originate 

 from a layer of hypodermal cells, but from only one or two. No divi- 

 sion of the tapetal nuclei could be detected in Potamogeton. The 

 growth and segmentation of the spirem in Convallaria are almost 

 identical with the same processes in Lilium ; the longitudinal splitting 

 of the ribbon is especially noticeable. In Potamogeton the process is 

 somewhat different. The number of chromosomes after reduction was 

 eighteen in Convallaria, seven in Potamogeton. In the formation of the 

 spindle the multipolar condition was evident in both genera. The 

 splitting of the chromosomes in the heterotypic division was in Conval- 

 laria similar to that in Lilium. The generative nucleus of the pollen- 

 grain is cut off by a distinct wall in Convallaria ; the division of the 

 nucleus probably takes place in the pollen-tube. In both cases the two 

 male nuclei, each enclosed within its own cell-wall, still remain attached 

 to one another, even when they enter the egg-apparatus. 



Cross-pollination and Self-pollination. — Mr. John H. Lovell f de- 

 scribes the mode of pollination — giving a list of the pollinating insects 

 — in a number of American species of Caprifoliace®, adding the follow- 

 ing general remarks. The rotate flowers of Sambucus contain no honey 

 and are sparingly visited by flies and pollen-collecting bees. Viburnum, 

 which has also a rotate corolla, but secretes nectar, attracts a large 

 number of bees, flies, beetles, and Lepidoptera. The corolla of Sym- 

 phoricarpus is bell-shaped, and is visited chiefly by wasps. The funnel- 

 shaped flower of Linnsea is adapted to slender flies. Lonicera alpigena 

 is a wasp-flower ; some of the species of Lonicera are visited by bees 

 in general, while others are pollinated only by humble-bees ; L. capri- 



* Bot. Gazette, xxviii. (1899) pp. 328-39 (2 pla.) 

 t Amr. Natural., xxxiv. (1900) pp. 37-51. 



