CO129-554-6 Hong Kong University- 1. Appointment of Dr. Chen Shas Yi as head of Chinese Department... 18-3-1935 - 28-10-1935 — Page 20

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A. H. CROOK

flowers. Sinnott and Bailey interpret these facts as showing that the family was originally arboreal, and that a subsequent reduction from the tree to the herbaceous type in certain genera has been accompanied by the development of specialised flowers. But bearing in mind the evolutionary lag in the tree form, it is surely more logical to suppose that the Leguminosae were originally herbaceous, and that those lineages which adopted the tree habit, put a brake, as it were, upon their own evolution and thus dropped behind the lineages which by remaining herbaceous, retained the power of mounting the ladder of floral specialization at a relatively rapid rate. The Leguminosae are by no means the only family in which the same process can be followed. The example which chiefly concerns us here, but to which Sinnott and Baily do not refer, is the Gramineae. The herbaceous grasses have, as a rule, extremely reduced flowers, but the flowers of the dendroid Bambuseae approximate much more closely to the usual monocotyledonous type."

So far so good. But surely Mrs. Arber must admit that the genera of the Bambuseae themselves ought to show this evolutionary lag more clearly in those where the generations are slow than in the annual or biennial forms; i.e. the flowers of those bamboos with a long period between their generations should approximate much more closely to the usual monocoty- ledonous type than the flowers of those which are annual or have a short period. But this is not so. Thus Dendrocalamus sp. with about a twenty- five or thirty year breeding period has numerous stamens; and Ochlandra sp., also with a slow breeding period, shows numerous structural variations from what might be considered the type form. While some of the annual bamboos, like Arundinaria Wightiana, which have therefore much more chance of undergoing the changes of genic outfit,' remain much closer to the usual monocotyledonous type. It must be noted, however, that many of the changes which do take place in the bamboos are in the nature of proliferation of the parts rather than reduction.

There is so much to comment upon and so many interesting details to quote in this volume that selection is difficult. The way in which cytology has come to the assistance of the observer and the field naturalist forms a very interesting branch of modern research. The early settlers in Americal were hard up for fodder grasses. Several British meadow grasses had to be imported. One, Phleum pratense L., introduced by Timothy Hansen, proved a very useful fodder grass. It was sent back to England a stronger and stouter plant under the name of 'Timothy grass.' Cytologists have now found that the returned emigrant has 42 chromosomes instead of the 14 with which the original wild 'Pilgrim Father' started out. Poa pratensis has also gone across to the States, and has become the famous 'Kentucky blue-grass.' Mrs. Arber makes the interesting suggestion that it, too, may be found to be a polyploid form i.e. a grass which has multiplied its chromosomes. This polyploidy is possibly initiated by crossing with some other species--though by what species these particular grasses were fertilised may now perhaps never be discovered.

Polyploidy, too, seems to have played its part in the production of that useful grass Spartina townsendi of which Mrs. Arber gives an interesting

The Hong Kong Naturalist.

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