206 SUMMARY OF CURRENT RESEARCHES RELATING TO 



few etiolated thalli bore exogenous antheridia which were otherwise quite 

 normal in structure and development. While a differentiated parietal 

 layer is necessary to an exogenous antheridium, its presence in the 

 endogenous antheridia which are peculiar to Anthoceros has been a 

 matter of speculation ; and Waldner's theory, that the antheridia of the 

 ancestral Anthoceros may have been exogenous formations, receives 

 support from this discovery. The laboratory culture appears to have 

 produced some reversions to an original type. 



Chemistry and Biology of Hepatics.* — C. E. J. Lohmann dis- 

 cusses the question of what are the protective substances that render 

 hepatics distasteful to slugs and other animals, giving a resume of the 

 work done by Stahl and others. Several hepatics have a strong aromatic 

 smell, or a sharp or bitter flavour, which are capable of being extracted 

 by alcohol ; and, until this has been done, these plants are avoided by 

 slugs. The author describes his attempts to determine the chemical 

 nature of these protective substances ; how he analysed the ashes and 

 found that silica affords no mechanical protection ; and how he deter- 

 mined that the immunity is not due to indigestible proteids nor to alka- 

 loids, but mainly to the ethereal oils as previously indicated by Stahl. 

 He details his analysis of these volatile oils, and describes the composi- 

 tion of the oil-bodies, etc. Ethereal oils are present in hepatics, absent in 

 mosses ; they appear in the early stages of growth, and have an aplastic 

 nature ; they are absent from spores and rhizoids (which are not easily 

 attacked), and tend to abound in peripheral positions. These are facts 

 that point to the protective function of ethereal oils, as also does their 

 absence from Anthoceros and Stasia, in which occur colonies of Nostoc 

 — an alga distasteful to slugs. 



Structure of some North American Hepatics.t — W. C. Coker 

 publishes some notes on the structure of Dumortiera, Blasia and Sp/uero- 

 carpus. Dumortiera hirsuta is of semi-aquatic habit, and if sufficiently 

 inundated has no air-chambers in its thallus ; but if less irrigated it 

 produces air-chambers which mostly disappear with age, and in snbdned 

 light its upper surface may produce a number of unicellular papilla?. 

 No trace of mycorhiza was found in the thallus. In Blasia pasilla it 

 was found that the No stoc -colonies are pervaded by a remarkable tree- 

 like out-growth of the thallus, which serves to abstract nourishment 

 from the alga. This ramifying hair appears to arise from the sub- 

 sequent growth of the original slime-secreting cell of the air-cavity. 

 This is explained by figures. In the sporangium of Splmrocarpus 

 terrestris occur peculiar sterile cells conspicuous for their bright green 

 chlorophyll-granules, which persist until the spores are ripe. They pro- 

 bably are the homologues of elaters, but are strikingly different. Their 

 function is photosynthetic. 



Odontoschisma in North America. $ — A. W. Evans gives the history 

 of the genus Odontoschisma. It contains about fourteen species, and 



* Beih. z. Bot. Centralbl. xv. (1903) pp. 215-56. 



t Bot. Gazette, xxxvi. (1903) pp. 225-30 (figs, in text). 



X Tom. oit , pp 321-48 (3 pis.). 



