204 SECTIONAL ADDRESSES. 



In addition we are getting together a collection of specimens showing 

 certain plants in all stages of their development, when growing wild under 

 very different soil and climatic conditions, all of which should be of great 

 value in careful ecological work. 



I may also mention here, as a further development of our herbarium 

 activities, which is proving of great practical value, that we have formed 

 a collection of fruits and seeds, which it is hoped in course of time will 

 be as comprehensive and complete as is the collection of the vegetative and 

 floral specimens in the General Herbarium. The value of this collection 

 to Mrs. Clement Reid and Miss Chandler in connection with their study 

 of recent fossil fruits and seeds has quickly been recognised. It has also 

 proved of great value for identifying samples of weed seeds, seeds accused 

 of poisoning stock, seeds used for adulteration purposes, and those used 

 as drugs. It is clear that the study of the seeds and their markings &c., 

 of all the species of a large genus, may also enable botanists to arrive at 

 some important deductions when making critical revisions. 



These special herbarium collections, together with the ' Herbarium 

 garden ' recently established at Kew, are, I think, very important develop- 

 ments for our Taxonomic and Economic studies. 



In the Herbarium garden,^^ foj. instance, many plants of botanical 

 interest — ' weeds,' perchance, to the ordinary gardener^can be grown, 

 and their development studied in detail. While from these plants 

 herbarium specimens can be prepared and preserved, showing not only 

 all stages in development, but also the character of the root system, 

 particulars which are usually so sadly lacking in specimens collected, 

 often in haste, in the course of some excursion or expedition. 



So much, then, for some of the modern developments and opportunities 

 in the domain of Taxonomic botany. Now let me turn to somewhat 

 similar problems which have recently been brought to our notice on the 

 Economic side. Very often it will seem that the matters to which I shall 

 refer belong rather to the domain of plant physiology, but since those to 

 which I propose to draw your attention are mainly concerned with plants 

 of economic importance they do, therefore, actually come within the 

 purview of what we generally consider to belong to the realms of Economic 

 Botany. 



In the first place I would draw your attention to the interesting 

 observations made by Dr. A. B. Stout and others on the flower behaviour 

 of Avocados,^* Persea gratissima Gaert. (Lauracese). These afford an 

 excellent example of the assistance that the botanist can render to the 

 grower and of the practical application of a remarkable botanical phe- 

 nomenon of great scientific interest. 



The Avocado Pear bears hermaphrodite flowers, but they exhibit a 

 daily rhythmic alternation of sexes reaching maturity for the entire plant. 

 This synchronous dichogamy apparently reaches a perfection of physio- 

 logical regulation to ensure cross-pollination, unknown in any other group 

 of plants. 



13 See Kew Bulletin, Appendix I. 1930, p. 44. 



1^ ' Memoirs of the New York Botanical Garden,' A. B. Stout, vol. vii. p. 145 (1927). 



