7l8 CHEMICAL PROCESSES IN THE PLANT. 



and medullary rays, where (this is not the case in the chlorophyll) it is always accom- 

 panied by sugar ; and it is evidently this latter substance which brings about the diffusion 

 from cell to cell, and at the same time furnishes the material for the formation of new 

 starch-grains. The sugar is the migratory product which takes part in the diffusion ; 

 the starch-grains ai e the temporarily stationary product. 



The distribution of starch and sugar shows moreover that they move from the 

 primary stem through the rachis of the inflorescence and the pedicels into the paren- 

 chymatous tissues, and penetrate into the young tissue of the flower, the growing fruit, 

 and the ovules, there to be employed in the production of cellulose. The distributed 

 starch collects more abundantly, especially in the immediate neighbourhood of those 

 layers of cells which afterwards form the hard endocarp and the solid testa of the seed, 

 in consequence of its being required here in greater quantity, disappearing also from 

 them after the complete development of these layers of tissue. 



The sugar and starch are conveyed through the funiculus to the ovules; they are 

 distributed through the integuments and the parts surrounding the nucellus ; and a large 

 quantity of sugar enters the growing endosperm, which supplies the material for the 

 formation of the oil which gradually accumulates, while fresh supplies of sugar are 

 constantly entering from without. In the growing embryo the cells are filled at a 

 certain period with fine-grained starch, which then entirely disappears and is replaced 

 by oil. All this indicates that the oil of the ripe seed of Ricinus is produced from the 

 starch and sugar which were transported to it from the assimilating organs during the 

 period of ripening ; and even the hard woody pericarp and the testa obtain their for- 

 mative material from those substances. The albuminoids which collect also in the 

 young leaves and from which the chlorophyll -granules are formed, as well as that 

 portion of these substances which accumulates in the seed as reserve food-material, 

 are transported from the stem by the sieve-tubes and the cambiform cells of the fibro- 

 vascular bundles. 



3. In the Leguminosae^ a very important part in the transport of the reserve proteid 

 substances is played by Asparagin. To demonstrate this, moderately thin sections are 

 placed in alcohol, and the saturation assisted by shaking. This mode is however applic- 

 able 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 under- 

 neath a little absolute alcohol. In this case the asparagin crystallises out round the 

 section ; while in the former case it is precipitated in the ceils 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. 



Luptnus luteus 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 have been quantitatively determined in the root, 

 hypocotyledonary portion of the stem, and cotyledons, at two stages of germination, the 

 last shortly before the cotyledons have thrown off the testa. 



The migration of the non-nitrogenous reserve-materials takes place in the usual 

 manner. 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. 



*. What follows is taken from a letter from Dr. Pfeffer. (Compare Book I. Sect. 8. p. 51 ; also 

 Jahrb. fiir wiss. Bot. VIII. p. 429 et seq.) 



[It must not be thought, however, that this substance is confined to this group of plants, for it 

 is very widely distributed, nor is it the only substance of this kind, for leucine and tyrosine have also 

 been detected in germinating seeds.] 



" Landwirthschaftliclie Versuchsstationen, vol. IX. 



