VI. 



A New Group of Flowering Plants. 



QUITE recently the study of a genus of flowering plants, in many 

 respects very peculiar, has led to most interesting results. 

 The genus Ccsitarina occurs chiefly in Australia, but is also met 

 with in Tropical Asia and Madagascar. In Australia it is known 

 as the She-Oak, but it is hard to understand why, unless, perhaps, 

 from its hard and heavy wood. The leaves are reduced to tiny scales, 

 borne in whorls on long green whip-like branches. The male 

 flowers are borne on spikes and consist of solitary stamens sur- 

 rounded by four bracteoles ; the female flowers are borne in capitula, 

 on twigs and branches of a very different age, and may often be 

 found in the old wood of thick branches. So unlike is the genus to 

 any other, that it has hitherto had a natural order to itself, styled 

 Casuarineae, and placed in the Apetalous group of dicotyledons. Its 

 affinities have always been regarded as most obscure, and the order 

 as very distinct from all other dicotyledons. 



At the close of last year, Dr. Melchior Treub, director of the 

 Botanic Gardens at Buitenzorg, Java, published the result of some 

 detailed researches, " Sur les Casuarinees et leur place dans le 

 Systeme Naturel." The results are startling, as may be judged from 

 the fact that they have led their author to place the Casuarineae by 

 themselves in a distinct sub-division of the Angiosperms. This is not 

 the first time that Dr. Treub has made the Annales du JavdinBotanique 

 de Buitenzorg the medium of a most important morphological commu- 

 nication. In 1 88 1, he communicated an important paper on the 

 Cycads, including many new facts relating to the development of the 

 macrosporangium, and in 1884 the first complete account of the 

 structure and life history of the prothallium of Lycopodium, which 

 he had succeeded in cultivating from the spore, and also found 

 growing naturally. It may be interesting to give a hviei resume of his 

 latest researches. 



At the outset, however, we may briefly review the structures 

 which are now generally regarded as of primary importance in the 

 classification of plants into large groups. A true appreciation of the 

 principle of the Alternation of Generations forms the basis of the 

 whole subject. 



The alternation is clear enough in the Ferns. It is a matter of 

 common observation that the tiny spores borne in great profusion, 



