ASSIMILATION AND METASTASIS. 



641 



is however applicable only when the asparagin is abundant ; when it is present in small 

 quantities it can still be demonstrated by placing a thin cover-glass on the sections, and 

 running in underneath a little absolute alcohol. In this case the asparagin crystallises 

 out round the section ; while in the former case it is precipitated in the cells in the 

 form of crystals. These can easily be recognised ; they are comparatively large, and 

 cannot be mistaken for other crystals which are formed in all plants on treatment 

 with alcohol, even where no asparagin is present, since these — which belong to various 

 salts, among others to nitrates — always remain very small and have an entirely different 

 appearance. 



' Lupinus liiteus is a good object for examination, and possesses the great advantage 

 that we have in its case an analytical investigation of Beyer's^ in which the organic 

 constituents and especially the asparagin hav-e been determined in the root, hypocoty- 

 ledonary portion of the stem, and cotyledons, at two stages of germination, the last 

 shortly before the cotyledons have thrown off the testa. 



' The following is what is known respecting the movements of the non-nitrogenous 

 reserve-substances. Starch is first of all formed in the hypocotyledonary portion and 

 root, then disappears and remains only in the endoderm, the rest being transformed 

 into sugar. Asparagin is first formed in the hypocotyledonary portion and root when 

 they are about 10 mm. long, but then rapidly increases in quantity while these parts 

 elongate ; and it is now formed also in the petiole of the cotyledons, and in the coty- 

 ledons themselves before they have become green and thrown off their testa, especially 

 in their lower part. The conditions remain the same during the whole of the time 

 that the reserve albuminous substances are being consumed. Asparagin is now found 

 in large quantities in the petiole of the cotyledons, almost to the extent of a saturated 

 solution (i part dissolves in 58 parts of water at 13° C), as well as in the hypo- 

 cotyledonary portion and in the stem as soon as it begins to grow. The asparagin 

 extends from the root and stem towards the punctum -vegetationis almost exactly as 

 far as the sugar, becoming finally, like the latter, less abundant. Beneath the coty- 

 ledons it is wanting in the pith, while in the stem it is as abundant there as in the 

 cortical tissue; it is never found in the vascular bundles. The asparagin also extends 

 into the petiole of young leaves as far as the base of the unfolding pinnae, as well as into 

 the lateral roots. As long as asparagin is formed out of the albuminous substances in 

 the cotyledons, it may also be found in the plant distributed as has been described ; but 

 when the cotyledons have been entirely emptied, the asparagin also disappears ; but this 

 does not happen in the case of Lupinus luteiis until several leaves have completely 

 unfolded. 



'The process is quite analogous in Tetragonobolus purpureus and Medicago tuber- 

 culata : in Ficia sati-va and Plsum sati'vum the presence of asparagin in the cotyledons 

 themselves cannot be proved with certainty, but is found at their base and usually also 

 in their petiole, although these plants produce decidedly less of it than Lupinus luteus. 

 Since moreover chemical analysis has established the production of great quantities ot 

 asparagin on germination in the case of a large number of other species of the order, we 

 may regard this substance as the form of transport for the albuminous substances 

 characteristic of all Leguminosse. Albuminous substances are moreover found m 

 these plants also in the thin-walled elongated cells of the vascular bundles ; and it is 

 quite possible that they are at the same time also transported by these structures. It is 

 evident that the source of the asparagin must be the albuminous substances, be- 

 cause the absolute amount of nitrogen remains the same during germmation ; and the 

 nitrogen of seeds is all or nearly all contained in their albuminous ingredients. 



'As to the influence of darkness on the formation of asparagin, we have diame- 

 trically opposite statements from Piria and Pasteur. The only certain pomt is that 



1 Landwirthschaflliche Versuchsstationen, vol. IX. 

 T t 



