276 SUMMARY OF CURRENT RESEARCHES RELATING TO 



uitratc per lioctarc, Avbicli accounts for only one-twentieth part of that 

 contained in the soil ; and this may possibly bo the source of a very 

 small proportion of the nitrates contained in plants, but by far the 

 larger portion must be formed in the plant itself. 



Keducing Properties of Seeds and Formation of Diastase.* — 

 By a series of experiments on the seeds of mustard, flax, lupin, barley, 

 &c., A. Jorissen claims to have determined that tlie reducing pro- 

 perties of seeds are independent of tlieir vegetative activity, and that 

 there is a relation between this phenomenon of reduction and the 

 production of diastase. It is possible that the presence of bacteria 

 in germinating seeds which contain no starch may bring about the 

 production of a diastatic ferment. 



Composition of Mineral Oil in relation to the Plants which have 

 produced it. t — A. Carnol states that the plants preserved in the soil 

 in the state of oil appear to have had very different properties, but a 

 nearly uniform elementary chemical composition. Experiments show 

 that the age of the oil and other circumstances at the period of its 

 formation were not the only factors in determining the properties of 

 the oil ; but that when all these circumstances have been identical, 

 different species of forest trees gave rise to oil of sensibly different 

 properties. 



B. CRYPTOGAMIA. 

 Cryptogamia Vascularia. 



Dehiscence of the Sporangia in Vascular Cryptogams. J — M. Le- 

 clerc du Sablon has investigated the mechanism of tlie dehiscence of 

 the sporangia in ferns and in Equisetacese. In the Equisetacefe the 

 dehiscence is the result of the unequal contraction of the lignified and 

 of the non-lignified parts of the cell-wall, and closely resembles the 

 process of the dehiscence of the anthers of flow^ering plants. In the 

 Polypodiacese, on the contrary, the cause is quite different, and the 

 dehiscence is due to variations in the pressure produced in the cells 

 of which the annulus is composed by the evaporation or absorption of 

 water, and is unconnected with any contraction of the wall itself. 



Development of Organs and Growth at the Growing Point of 

 Dorsiventral Ferns.§ — L. Klein has examined the apical growth of 

 dorsiventral ferns in fifty species belonging to nineteen genera. In 

 opposition to the prevalent view, he finds, in all the species, notwith- 

 standing a pronounced bilateral structure, a three-edged apical cell. 

 Apparently two- and sometimes also four-edged apical cells occur only 

 temporarily as the result of an abnormally placed segment-wall. La 

 Pteris aquilina, on the other hand, the apical cells, which must typically 

 be two-edged, were fdund to be very frequently three- and even four- 

 edged. These were formed in the way described by Hofmeister, while 

 the tliree-edged apical cell of other ferns shows no definite origin, 

 but usually has one corner directed upwards. The division of the 



* Bull. Acad. E. Sci. Btlg., viii. (1884) pp. 521-4, 550-5. 



t Comptes Rendus, xcix. (1884) pp. 253-6. 



X Bull. Soc. Bot. France, xxxi. (1884) pp. 292-5. Cf. ante, p. 91. 



§ Bot. Ztg., xlii. (1884) pp. 577-87, 5D3-604, 609-15, 625-35, 641-9 (1 pi.). 



