Mav 



I'^^QS] 



NATURE 



Iread " ; but if I can elicit some definite scheme from Prof. 

 Armstrong;, I .shall regard my own dialectic annihilation as a 

 -mall price to pay for the ultimate yain. I). S. T. ('.RANT. 



Chemical I.alioralory. Lahore, I'nnjali. 



A Lecture Experiment. 



To show that chlorine will attack mercury, some mercury was 

 shaken up in a covered gas jar filled with chlorine. On shaking, 

 ihe sides of (he jar and also the cover-glass became coated with 

 a continuous film of mercury, as though the inside were silvered. 

 .After a short time, the film was eaten through, and patches of the 

 white chloride produced. I have not seen this efltct noticed 

 ill Ixioks, .so il may be worth while to call attention to it. 



C. J. Woodward. 



Municipal Technical .School, Hirmingham, .\pril 25. 



viTAi.rry of seeds. 



'"PHE duiatinn of the \ itality (if seeds is perhaps the 

 ^ most important of the various phenomena of plant- 

 life, especially when considered in connection with the 

 introduction into a countiy of the economi'- plants of 

 other countries. It is a subject that has eng^aged at- 

 tention from very early times, and the literature relating 

 thereto is considerable. Much of this, however, is of a 

 traditional and unpractical character ; but even if we 

 confine ourselves to the demonstrable, or demonstrated, 

 the subject is almost inexhaustible. There is such an 

 infinity of variety in the behaviour of seeds under 

 different conditions, that it is impossible in a short 

 account, such as this must be, to do more than convey a 

 general idea of the subject. Perhaps the best way to treat 

 the question, apart from technicalities, is to consider 

 the vitality of seeds under ordinary, and under extra- 

 ordinary, conditions. In the development and germinatfftn 

 of seeds, there is, in a sense, usually a period of gestation 

 and a period of incubation, as in oviparous organisms of 

 the animal kingdom; and the duration of these pciods 

 is within definable limits, under ordinary conditions, 

 though seeds do not exhibit the same fixity of time in 

 regard to development and vitality as eggs. The embryo 

 of a seed is the result of the impregnation of the female 

 ovum in the ovary or young seed-\essel, by the male 

 element, generated in the anthers ; and in the mature 

 state this embryo may fill the whole space within the 

 skin, or testa, of the seed, as in the bean and acorn; or 

 it may be a comparatively minute body, as in wheat, 

 maize, and other cereals; the rest of the seed being filled 

 with matter not incorporated in the embryo. The 

 difference is one of degree in development. In the one 

 case, the growing embryo h;is absorbed into its own 

 system, as it were, before germination or the beginning 

 of the growth of the embryo into a new plant, the whole 

 of the nutrient materi;il provided in the seed for repro- 

 duction ; whereas, in the latter case, the |)rocess of 

 .disorption and utilisation of the "albumen," or nutrient 

 matter, takes |)lace after the seed is detached from 

 the parent plant, and during the earliest stage of 

 growth of the new plant ; so tli;it the plant is nourished 

 until it has formed organs capable of assimilating 

 the food obtainable from the atmosjihere and earth. 

 Between these two extremes of development of the 

 embryo, or future plant, before organic connecti<m with 

 the parent ceases, there is every conceivable degree and 

 variety ; and, as will presently be explained with 

 examples, some |)lants are viviparous, in the sense that 

 the embryo commences active life before being severed 

 from the parent, so that when this occurs the plant is in 

 a ])osition to draw its sustenance from unassimilated or 

 inorganic materials. Now it is a curious and unexplain- 

 able fact that certain seeds exhibiting the extremes 

 of embrvoiial development, instanced in the bean and 

 \vheat, are equally retentive of their genninative power. 

 The longevity, if it may be so called, of seeds is ex- 



NO. 13.^1. VOL. 52] 



emplified in " exalbuminous " seeds as well as in 

 "albuminous" seeds of every degree. It should be 

 mentioned, however, that the difference is not so mu( h 

 one of assimilation or development as of the earlier 01 

 later transfer of the nutrient matter of the seed to the 

 embryo or planllet. .Assuming the perfect maturation of 

 a seed, certain conditions are necessary to quicken its 

 dormant vitality ; and the two principal factors are heal 

 and moisture, var)ing enormously in amount for different 

 plants, and acting much more rapidly on soine seeds than 

 on others, even when the amount required is much the 

 same. Neither under natural nor under artificial con- 

 ditions will some seeds retain their vitality more than om- 

 season ; and all the resources of the accumulated exper: 

 ence of seed-importers from distant countries are insuffi 

 cient in some cases to maintain their vitality. It is not 

 altogether because the interval between the dispersal and 

 the germination of the seed, under ordinary conditions, is 

 necessarily longer ; but rather because in the one case the 

 conditions under which a seed will germinate are much 

 more restricted than in the other. Let us now examine 

 the natural conditions under which seeds are commonly 

 produced and dispersed, in relation to the retention of 

 their vitality ; and we shall learn how much more it 

 depends on their nature, or natural means of protection, 

 than on the seasons. .An oak tree sheds its acorns in 

 autumn, and the leaves which fall afterwards afford them 

 some protection from frost and excessive dryness. But 

 the leaves might be blown away from one spot, and the 

 acorns exposed to intense frost or drought, either of which 

 will speedily kill them. In another spot the leaves may 

 drift into thick layers, with an excessive accumulation of 

 moisture, causing decay of the underlying acorns ; and 

 there are many other unfavourable conditions which may 

 destro)' the vitalit\- of the acorn. It is apparently ini 

 possible, however, to preserve an acorn's vitality by any 

 artificial means for more than one season. 



The scarlet-runner bean loses its germinative power 

 on exposure to coni|xiiatively slight frost, the degree 

 depending upon the amount of moisture in it ; yet it v\'ill 

 retain its vitality for an almost indefinite period under 

 favourable artificial conditions. In both of the examples 

 given, germination would naturally follow as soon after 

 maturation as the conditions allowed. The seeds of the 

 hawthorn behave differently. Each haw contains nor- 

 mally three to five seeds, every one of which is encased 

 in a hard, bony envelope, in addition to its proper coat 

 or testa. Committed to the earth, and under the most 

 favourable conditions, these seeds do not germinate till 

 the second year, and often not so soon. In this instance 

 prolongation of vitality is probably due in some measure 

 to the protective nature of the shell enclosing the seed. 



Returning to seeds in which the enibr)i) or plantlet 

 forms only a very small part of the whole body, wheat 

 may be taken as a familiar and easily observed illustra- 

 tion of a seed, the vital energy of which requires vcr) 

 little to stimulate it into active growth ; and yet this 

 same seed, having no special protection in the way of 

 coating, will retain its vitality as long, perhaps, as any 

 kind of seed, if not under the influence of moisture. 

 The primary condition to the preservation of vitality 

 in a seed is perfect ripeness. Unripe seeds of many 

 kinds will germinate :ind grow into independent ])lants if 

 sown immediately after removal from the parent. The 

 facility with which immature wheat will germinate is 

 most disastrously exemplified in a wet harvest, when the 

 seeds will sprout while the corn is standing or in sheaf ; 

 thus destroying more or less completely the value of the 

 grain for flour, as the starch or flour is consumed in the 

 (levelopment of the embryo, or what is left is so deterio- 

 rated by chemical change that it is not good for food. 

 There is perhaps no other seed more susceptible to- 

 moisture, and none less affected by dryness, or by heat 

 or cold in the absence of moisture. 



