August 4, 1898] 



MATURE 



m 



mutual dependence of embryo and endosperm in Hordeutn 

 vulgare. In it the proportionate shares taken in the endospermous 

 depletion are evaluated for (l) the embryo, (2) the amyliferous 

 part of the endosperm, (3) the so-called " aleurone-layer " 

 (Kleherschitkt). The possibility of some of the changes being 

 due to enzymes pre-existent in the seeds is considered, as also 

 of any action being due to micro-organisms in experiments 

 with degermed endosperms. The conclusions are drawn from 

 results given by very many experiments in widely-varied con- 

 ditions. 



Great difficulty was found in the just appreciation of the effects 

 of micro-organisms, for, although their influence on intact 

 seeds is minimal, yet their action on the endosperm bared 

 through degermation produces changes in the cells hardly dis- 

 tinguishable from such as would be induced by the cells them- 

 selves, on (he assumption that they had livmg contents. 



No antiseptic reagent could be found with such differential 

 action as to inhibit, or materially retard, the growth of micro- 

 organisms, while not hindering normal development of the seed- 

 ling. But extreme refinements for avoiding air-sown organisms 

 are useless, since complete initial sterilisation of the exterior 

 of the grain cannot be ensured. Differentiation of autonomous 

 action of the tissues from that of extraneous organisms was 

 much aided through study of the action of similar organisms on 

 undoubtedly dead tissue. 



To ascertain the self-depletive power of endosperms from 

 which the embryo had been removed, a method was adopted 

 almost identical with that described in the paper of 1890 {loc. 

 ii't.). The endosperms were placed with their proximal ends 

 downward in small holes in a very thin mica-raft, which was 

 then floated on water so as to just submerge the endospermous 

 surfaces laid bare through degermation, every facility being 

 thus given for outward diffusion of products of change. This 

 method is preferable to Hansteen's plan of affixing the grains 

 to plaster-columns standing in water. In these conditions slow 

 changes undoubtedly occur in the degermed seeds, these being 

 due neither to influence of micro-organisms, nor to enzymes 

 pre-existent in the grains. The changes are very much slower 

 than those of normal germination, but are of the same order, 

 and are undoubtedly due to autonomous action of some part of 

 the endosperm. 



There is firstly a tendency for the "aleurone-layer" to se- 

 parate from the underlying amyliferous cells through cytohydro- 

 lysis of the membranes of the latter. This action commences 

 on the dorsal side of the grain near the apex of the scutellum, 

 extends gradually in well-defined directions, and invades slowly 

 the more deeply-seated parts of the endosperm, producing a 

 partially-mealy consistence of the cell-contents. This cytohydro- 

 lysis is followed after some days by a more or less partial erosion 

 of the starch-granules underlying immediately the "aleurone- 

 cells." Til is erosion is, however, very different from that effected 

 by the embryo through the enzyme secreted by its columnar 

 epithele. The difference between these two modes of erosion is 

 clearly shown in the accompanying prints. 



These changes in the degermed seeds are without doubt self- 

 induced, since it is impossible to produce them in endosperms 

 that have been demonstrably killed through submersion in chlo- 

 roform-water for twenty-four hours. It is also certain that the 

 aciicm is initiated by the "aleurone-layer," and not by any 

 autonomous action of the amyliferous cells, since no such 

 changes can be induced in this portion after deprivation of 

 its "aleurone-layer." 



Although the statement made in 1890 that the amyliferous 

 cells possess no self-depletive power, is true, the one affirming 

 that the endosperm as a whole is passive during germination 

 requires correction, since the "aleurone-layer" shares with the 

 embryo in preparing the reserve materials for the seedling. 



As an active agent in amylohydrolysis, the " aleurone-layer " 

 seems to play a subordinate part to the embryo ; its principal 

 function appears to be cytohydrolytic. Certainly an embryo 

 f^rafted on an endosperm, the "aleurone-layer" of which has 

 Ixien killed, cannot induce an action comparable in intensity 

 with that produced through joint action of a living embryo and 

 a living "aleurone-layer." This is not due to deficiency in 

 amylohydrolytic {xjwer of the embryo, but to the fact that the 

 embr>'o has relatively small cytohydrolytic power, so that the 

 action of its diastase, owing to the low dilfusibility of the latter, 

 is not effective as long as the membranes of the amyliferous cells 

 are undestroyed. 

 The view put forward in 1890, that the whole endosperm is 



NO. 1 501, VOL. 58] 



passive during germination, was mainly founded on experiments 

 in which livine embryos had been " grafted " on endosperms 

 previously soaked for several months in strong alcohol, a treat- 

 ment then believed to ensure complete loss of potential vitality 

 of the " aleurone-layer." Such treatment is now known to be 

 insufficient to destroy with certainty even the potential life of 

 the embryo, for barley-seeds have been germinated that had 

 been continuously soaked in strong alcohol for many weeks, and 

 there is reason to believe that the " aleurone-layer " is even 

 more resistant to adverse conditions than the embryo. 



The conclusion that the amyliferous cells are incapable of 

 initiating any changes in themselves as deduced from physio- 

 logical experiments, is strongly supported by cytological 

 observations. A method is described in the paper by which 



Fig. I.— Sub-scutellar erosion of starch produced by the embryo. Here the 



■ the granule. These pits 



action commences with general pitting of 

 enlarge, and thus break up the granule 



Fig. 2. — "Sub-aleuio;iiu ^\^^von. Here no preliminary pits are formed, 

 but large rijts are produced, and the granule undergoes concentric or 

 irregular dissolution. 



these cells can be cleared of their closely-packed starch granules,, 

 so that the nuclei can be readily discerned. During develop- 

 ment of the amyliferous cells of the endosperm their nuclei 

 become extremely deformed, owing to the increasing pressure of 

 the starch-granules, and are very often disintegrated. It is 

 difficult to believe that cells in this condition can functionate, 

 even if there were no confirmatory evidence such as is afforded 

 by the physiological experiments described. 



It is very probable that the "aleurone-layer" possesses a 

 function additional to that exercised during germination, but 

 which can hardly fail to be very important. Its cells, which 

 undoubtedly contain living elements, constitute the outermost 

 peripheral layer of an otherwise dead endosperm, and this wouldl 



