Sept. 14, 1883.] 



KNOWLEDGE • 



163 



grooved, and the style runs up it. When a corolla is 

 fading, a gentle pull will draw out the style, and it is 

 found to be very slender. The filaments are deep orange 

 red, the petals bright pale yellow. This makes an elegant 

 contrast, and the plant exhales a delicious scent of a honey- 

 and-ginger character. To see it to perfection it should be 

 placed in a sitting-room window, or cool corner of a con- 

 servatory, as soon as any of the flowers begin to open. With 

 such treatment it will display its beauty for several days, 

 while in a hot place the corollas that first open fade before 

 the others arc ready, and a shabby appearance is produced. 

 A honey fluid drops freely from the stigmas, and is very 

 viscid. Taking some of the pollen and putting it in this 

 fluid slightly diluted with water, generally succeeded on a 

 bright day in inducing some of the pollen cells to sprout. 

 A.t first a little projection was found, as at B. This was 

 quite clear and glassy. It gradually elongated into a tube, 

 a clear space being always in advance, which showed the 

 vital action to be in the tube walls. They were not puslied 

 forward by the granular matter, but that waited for their 

 growth, and then entered into the space provided for it. A 

 represents one of the best developed tube.-? formed in the 

 course of a few hours ; C, a group of pollen cells and tubes, 

 one cell emitting a tube on opposite sides. Very often, 

 instead of forming a regular-shaped tube, the pollen cell 

 allowed the granular matter to escape in the forms shown 

 by two cells, one on the right and the other on the left in 

 the figure. That on the left was a mess from the beginning 

 — that on the right began well and c^nded in a zigzag muddle. 

 A represents the nearest approach to the right thing, but 

 probably the tube is more slender when it grows out of the 

 cell under natural conditions. 



Botanists distinguish the outer coating of the cell as 

 cxtine, and the inner layer as intinc. The intine forms the 

 tube, and the granular matter undergoes a development 

 which fits it for the work of fertilisation. The time it 

 takes for a pollen tube to develop varies with different 



plants. Ultimately it gets into an ovule through a small 

 entrance (micropyle), and proceeds to its special work 

 more quickly or slowly, according to the nature of the 

 plant. Sachs observes : — " The time that intervenes 

 between pollination and the entrance of the pollen tube 

 into the micropyle depends not only on the length of the 

 style, which is often very considerable (as in zea and 

 crocus), but also on the specific characters of the plants. Thus, 

 according to Hoffuieister, while the poUen tubes of crocus 

 vernus only requires from twentj'-four to seventy -two hours 

 to penetrate the style, which is from five to ten centimetres in 

 length,* those of Arum maculatum take at least ti\^e days, 

 although the distance they have to go over is scarcely more 

 than 2 or 3 mm.f, and those of Orclndea: require ten days, 

 or even several weeks or months, during which time the 

 ovules first become developed in the ovary, or even are not 

 formed till then." When the pollen tube has reached its 

 destination, the development it induces may be quick, 

 or, as is the case with many trees, may take weeks, or 

 months. In the meadow saflVon (Colchicum antnmna/e) 

 Hoflmeister finds the pollen tubes enter at the latest at 

 the beginning of November, but it is not tUl the May fol- 

 lowing that the formation of the embryo begins. 



The experimenter with pollen grains must not expect 

 uniform success. Operating with those of the llcdychium 

 several failures were encountered, and on a dull day with- 

 out any instance of success. If the pollen cell shows no 

 inclination to make the little bulge that is the commence- 

 ment of a tube in an hour or so, it is well to begin again 

 with a fresli lot. The pollen grains should not be too 

 thickly crowded, and the viscid fluid only thinned just 

 enough to flow freely amongst them. In some plants the 

 fluid of the stigma may not require this, and it is as well 

 to try it in the state in which it is exuded. 



* 10 centimJitres = 3'937 inches. 



+ A nlillim^tl■e — 039 of an inch ; 2G are rather more than 1 in. 



