114 HYBRIDISING AND CROSS-BREEDING. 



Allen Maclean, and the result of the experiments made go to 

 prove that, as had previously been surmised by Herbert and 

 others, the fecundating tubes emitted by the pollen are not 

 continuous, but that they grow by the addition of new cells, 

 and in Tigridia are propelled through the tissues of the style 

 at the average rate of one inch in six hours, although the 

 rapidity of its growth and the consequent impregnation of the 

 ovules is dependent on atmospheric influence. In direct 

 sunlight and a humid atmosphere the growth increased to one 

 inch in two hours. In their passage down the style (we are 

 told) they are nourished by the juices of the style-cells, and 

 even by the cells of the ovule itself, when that body is reached. 

 The pollen-tube pushes the embryo-sac before it for a short 

 distance i.e., indents it without perforation; but after a time 

 the contents pass into the embryo-sac whether by endosmosis 

 or direct injection we are not tald and an embryo is formed. 

 When we are told that the moist cellular tissues of the style 

 afford nourishment to the pollen-tubes, one naturally wonders 

 how they are nourished in Conifers, where there are no styles. 

 Now what do we find ? Why, a drop of clear mucilage exuded 

 from the apex of each ovule, and evidently intended as a 

 special provision to secure fertilisation, and to afford nutriment 

 for the elongating pollen-tubes in the absence of the supply 

 which, in the usual course of things, is afforded by the muci- 

 laginous tissues of the style. (See Conifers.) 



Facilitating the Growth of Pollen. M. Beer, Curator of the 

 Botanic Gardens at Vienna, mentions that M. Hooibreuk, 

 one of his assistants, has adopted the following process, 

 previously suggested by Gaertner, for successfully facilitating 

 the fertilisation of plants. The stigma of each flower to be 

 operated upon is touched with a camel's-hair pencil dipped in 

 honey, or better still, with honey and the pollen of the plant 

 destined to be the male parent. This process has succeeded 

 admirably in the case of fruit-trees. The use of the honey is 

 doubtless to retain the pollen - grains on the stigma- and 

 according to the evidence of Max Wichura, the moisture 

 facilitates the growth of the fecundating tubes. Honey is 

 supplied naturally in some cases, of which the common Agave 

 and Hoy a carnosa or "wax-plant" are familiar examples. 

 Propagators can generally obtain honey conveniently and in 

 sufficient quantities from the tubular flowers, as in the case of 

 Fuchsias, Achimenes, and many Other plants, and the plan 

 here recommended is worth adopting in the case of Muscat 

 Grapes or early Peaches and Nectarines. 



How Fertilisation takes place, Prof. Bentley, in his ' Manual 



