198 SCIENCE PROGRESS 



as in Agathis and Podocarpus and simple polyembryony result- 

 ing from the fertilisation of several eggs, as in Cycads, are 

 considered to be advanced features. Grouped in respect to 

 the pro-embryo structure, the assumed line of progressive 

 specialisation and advance is also that of numerical decrease 

 of the Cotyledons, whilst the presumably primitive genera are 

 those with dwarf shoots. 



Chamberlain, in considering the hving Cycads, upholds the 

 view that the Cycadophyta have been derived from the Ferns 

 by way of Cycadofilices, directly, or as a branch from the 

 Bennettitales, and that this Hne of evolution is distinct from 

 that of the Coniferophyta, to which probably the Gnetales and 

 Angiosperms are connected by way of supposed extinct her- 

 baceous ancestors. 



In a third paper by Wieland, the distribution of the 

 Cycadeoids is considered and their affinity to other groups 

 of seed plants. Of these latter the Gnetales, Angiosperms, and 

 Conifers are regarded as the most remote, whilst the Cycads, 

 Cycadofilices, and Cordaitales are held to be the most nearly 

 allied in the order named. 



In this connection a recent paper by Scott is of interest 

 {Brit. Ass. Rep.). This author suggests that the Pteridosperms 

 and Angiosperms have always been distinct from any known 

 Phyla of Vascular Cryptogams, and regards the fern-like 

 features of the Cycadofilices as no evidence of affinity. 



Yampolsky {Amer. Jour. Bot.) describes and figures various 

 types of hermaphrodite flowers of Mercurialis annua. In place 

 of the two carpels or 8-20 stamens of the normal flowers, 

 these showed in some cases only one carpel with a group of 

 stamens replacing the second. In other flowers three carpels 

 were present accompanied by 1-6 stamens, or structures which 

 were intermediate between stamens and carpels. 



Anatomy. — Experimental work carried out by Snow {Bot. 

 Gas.) indicated that the intervals between the successive 

 diaphragms of a water plant {Scirpus validus) increased with a 

 decrease in the rate of growth, and the increased intervals 

 observed under low pressures was attributed to this cause. 

 Diminished pressure appeared to have no effect either on the 

 number or size of the air-chambers, and the conclusion is 

 drawn that the occurrence of air-spaces bears no relation to 

 low oxygen-pressure. 



Barrat and Browne both contribute papers on the anatomy 

 of Equisetum {Ann. Bot.). The former finds that the sporeling 

 of E. arvense is at first protostelic, later becoming siphonosteHc. 

 The existence of secondary thickening at the nodes of E. 

 arvense and E. maximum is denied, whilst the sporangiophores 

 are regarded as organs sui generis, and not as fertile leaves. 



