HYBRIDISING AND CROSS-BREEDING. 109 



pollen carefully shaken from the anthers during dry sunny 

 weather when perfectly ripe, and wrapped neatly in silk-paper, 

 will retain its quickening or vivifying powers for days, weeks, 

 or even months together. Silk-paper or tinfoil is the most 

 convenient covering in which to preserve pollen-grains; but 

 if it is to be kept for a great length of time, it should be her- 

 metically sealed in glass -tubes, which can be bought at any 

 chemist's. One end of the tube is sealed by holding it near a 

 gas jet, and using a blow-pipe to intensify the power of the jet. 

 After the end is sealed, allow it to cool before the pollen is 

 enclosed, then shake it down to the sealed end, and seal the 

 other end in like manner. If you are not familiar with the use 

 of the blow-pipe, seal the ends of the tubes with hot sealing- 

 wax. Pollen may be mounted in dry cells, and covered by a 

 strip of thin glass, as used by microscopists, air being excluded 

 by Canada balsam and so treated, retains its vitality ; and there 

 is the additional advantage that it can be often examined 

 under a low power, and any change noted. On no account 

 must the pollen have been wetted before it is enclosed, for on 

 its being gathered in a dry and fully - developed condition 

 depends its keeping qualities and quickening action. As yet 

 we know but little as to the comparative vitality of either seeds 

 or pollen, and experiments with pollen are especially to be 

 desired. The late Dean Herbert, in alluding to this subject 

 nearly forty years ago, remarked that " old pollen which has 

 been kept perfectly dry may act so as to fertilise, but that 

 which has once been damp cannot do so." The pollen of 

 Cerens gmndifiorus, kept for six weeks in a bit of paper, enabled 

 Mr H. Brown to obtain a hybrid between that species and 

 Phyllocactus Jenkmsbnii. Linnaeus found that the pollen of 

 Jatropha urens, six weeks old, was but little impaired in its 

 action. 



Wichura (see Jour. Royal Hort. Soc., 1866, vol. i. p. 58), in 

 speaking of the pollen of Willows (Salix), remarks that fresh 

 pollen, placed in a weak solution of honey and water, began to 

 emit pollen -tubes in the course of ten or twelve minutes. 

 Pollen of Saltx silesiaca, eight days old, seemed almost as 

 potent as ever, but in twenty-eight days the traces of vitality 

 were very slight ; while that of S. cinerea had become weak in 

 sixteen days. On the whole, it seems that pollen of Willows, 

 if kept in a dry, cool, shady place, is efficient when fourteen 

 days old, and it may be implicitly trusted at eight days old. 

 Mr Anderson-Henry observes that the pollen of Rhododen- 

 drons is potent after being kept for six or eight weeks, and 

 pollen of Clematis Jackmanii was found to be potent after 



