746 EEPOKT— 1892, 



Hymenophyllere, in wliicli the antheridia are directly sessile on tlie filaments, 

 wiiilst the archegonia stand upon a ciisbion of cell-tissue, the archegoniophore, pro- 

 duced by the division in a longitudinal direction of a prothallus-filament. This 

 female plant in Buxhaumia is an archegoniophore, with envelopes composed of a 

 number of leaf-like structures without chlorophyll, which correspond with the 

 single envelope leaf of the male plant. Only one archegonium is developed. 



The sexual generation of Buxbaumia possesses, then, an extremely simple con- 

 struction, and in my opinion exhibits the nearest approach known to the ancestral 

 form of the mosses. One might, of course, conjecture that this simplicity of con- 

 struction is a reduction from a more complex ; hut against this view may be urged 

 that Buxbaumia possesses characters which separate it from the other mosses, and 

 which remind us of the liverworts, chiefly of a low stage in development. These 

 characters are : — 



1. Form of antheridium ; which is very different from that of Bryineoe, and 

 corj-esponds with that of many liverworts. 



2. The arrangement of the cells in the leaf. 



3. The fact that the marginal cells of the leaf normally grow out into proto- 

 nema-threads, which shows that the leaves are merelj^ expanded protonemata, an 

 assumption which is supported by other facts. 



The author believes, then, that Buxbaumia has preserved in its sexual genera- 

 tion the primitive characters, and is a very old type. 



4. On the Cause of Phi/siological Action at a Distance. 

 By Professor L. Errera (Brussels). 



Most vegetable organs .are sensitive to the influences of their environment, and 

 respond to these stimuli, as long as they are capable of growth by bending in 

 a definite direction. In fact, they generally i'eel asymmetrical distribution of 

 matter or energy around them. Thus the geotropic, heliotropic, hydrotropic, 

 haptotropic curvatures arise which are familiar to vegetable physiologists. 



But the very interesting phenomena described two years ago by Elfving did 

 not appear to belong to any of the known categories, and led this distinguished 

 botanist to the assumption of a new force revealing itself by ' physiological action 

 at a distance,' as he terms it. 



He found that pieces of iron, and to a less degree of zinc or aluminium, as well 

 as different organic substances — sealing-wax, rosin, roots of living plants — attract 

 the growing, sporangium-bearing filaments of P/n/comi/ces nitens, a well-known 

 fungus belonging to the Mucorini. All other metals tried by Elfving were in- 

 active, whereas the filaments of Phycomyces itself showed a mutual repulsion. 



The latter fact, which I had often observed, I always ascribed to negative 

 hydrotropism. So the question arose whether the attractions discovered by 

 Elfving are not due to a similar cause. For, just as we know that a surface 

 which emits moisture repels the Phtjcomyces filaments, it seemed probable that 

 moisture-absorbing substances should produce the reverse efiect and attract them. 

 IVow iron certainly absorbs aqueous vapour whilst rusting, and its peculiar action 

 on Phycomyces might thus be simply a case of hydrotropism. 



I have tested this view by a great number of experiments, and I submit for 

 the inspection of tlie members of this section photographs showing the behaviour 

 of Phycomyces towards different substances. This theory enables one not only to 

 explain the known facts, but it also permits one to predict unknown ones. 



It is easy to demonstrate that any modification of iron which lessens its capa- 

 city of rusting at the same time diminishes its attraction on Phycomyces : polished 

 steel scarcely attracts, and nickelled steel does not do so at all. 



China clay, which is very hygroscopic, attracts energetically, but china exhibits 

 no attraction. One of the most striking instances is that of agate and rock-crystal. 

 Although both are essentially formed of silica, the Japanese physicist Ihmori ' has 

 shown that the former is very hygroscopic, whereas the latter is not so. And, .18 

 •was to be foreseen, agate strongly attracts the I'hyconiyces, though rock-c)'ystal 



' Wiedemann's Annalen, 1887, xxxi. p. ]006. 



