115 



is connected on the side ['' with the tissue of the sheath leaf and it is worth 

 noting that this sheath, even in so young a stage of blade differentiation, must 

 liave finished its work since the tissue is entirely impoverished and begins to 

 be full of holes (I). 



While therefore in the Gramineae the accessory apparatus, which with 

 too deep sowing brings the vegetative tip into the abundantl}^ aerated par- 

 ticles of soil, consists in the elongation (observed up to 9 cm.) of the lowest 

 internode and, in case of necessity, also of the one above it, we find in the 

 Leguminoseae and other dicotyledons a different arrangement. In beans, 

 for example, we notice first of all an increased elongation of the hypocotyle 

 corresponding to the need, so that finally, with very different depths of sow- 

 ing, the growing tip of the stem in all plants is found at approximately the 

 same height. Naturally the strength of the plant from the same kind of seed 

 is decreased as the depth of sowing is greater. The more the hypocotyle must 

 be lengthened, in order that its upper part, comparable to the curved back 

 of the burden-carrier, can break through the load of the soil and bring the 

 cotyledons to the light, the more reserve substances will be used up. It is 

 therefore very evident that plants coming from greater depths are weaker 

 even if they have not lost reserve substances in the seed through strong 

 intra-molecular respiration. Such will be the case, however, if continued wet 

 weather sets in after too deep sowing so that a shortage of oxygen results. 



The experiments by Godlewski and Polzeniusz^ show what amounts of 

 reserve substances can be lost through intra-molecular respiration and the 

 formation of alcohol. Sterilized peas, in evacuated air, produced in the first 

 period almost as much carbon dioxid as in normal respiration in the air. 

 The whole amount exceeded 20 per cent, of the original dry substance of the 

 seed. The amount of alcohol formed corresponds to that of the carbon 

 dioxid. Only during the sixth week did the production of carbon dioxid 

 cease in the peas which lay in sterilized water and up to that time possibly 

 40 per cent, of the dry substances present had been broken down to alcohol 

 and carbon dioxid. This is also the case in grains. In grains the action of 

 the secondary roots on the nodes of the stem counteracts this weakening. 

 In legumes a similar process of self assistance can now take place, since, as 

 Wollny proved, adventitious roots are formed from the over-elongated 

 liypocotyle member. He observed this on the parts of the stem which had 

 been covered with soil, not only in field beans, but also in peas, sweet peas, 

 lentils, lupines and plants of other families, — rape and sunflowers. But the 

 legumes often are not capable of using such an a'ccessory apparatus since, 

 with normal depth of sowing and capacity for germination, they easily suc- 

 cumb to other dangers which will be described in the section on "condition 

 of hard shells." 



1 Godlewski unci Polzeniusz, Ueber Alkoholbildung bei der intramolekularen 

 Atmung hoherer Pflanzen. Anzeig. Akad. d. Wiss. Krakau, cit. Bot. Jahresb. 1897, 

 p. 142. 



