NA TURE 



[May 2, 189: 



The kind of vivipan- exhibited by the wheat is occasion- 

 ally obsencd in various other plants : and sometimes 

 the seeds of pulpy fruits germinate in the fruit. There 

 is also a class of plants in which \ivipar>' is normal. 

 Prominent in this class are the manjjrovcs \Rliizopliort-(r, 

 &c.) of muddy sea-shores in the tropics. In these plants 

 there is a remarkable adaptation to conditions, which 

 ensures their reproduction. From the ver\ inception of 

 the embryo there is no apparent interruption of active 

 vitality in its development and germination. In the 

 earliest stage the cotyledons or seed-leaves arc formed, 

 and the radicle or future primary root is represented by 

 a very small point. When the former have attained their 

 full development, which is not great, the latter begins to 

 ^ow and rapidly increases in size. Each fniit or seed- 

 vessel, it should be mentioned, contains only one seed, 

 the rootlet of which points to the apex of the fruit. 

 Soon this rootlet pushes its way through the apex of the 

 fruit, and grows into a spindle-shaped body of great 

 density and length ; the cotyledons or seed-leaves re- 

 maining partly inside the fniit, and acting as an organ of 

 absorption from the parent plant to nourish the seedling. 

 In Rhi-iyphora muironnla this radicle attains a length of 

 two to three feet, and the seedling eventually falls, and by 

 its own weight penetrates and sticks in the mud, leaving 

 the fruit, containing the exhausted cotyledons, attached 

 to the tree, where it dries up. .Another .singular adap- 

 tation to conditions is the vital development of the 

 seeds of aquatic plants which ripen their seeds on or 

 under water. Vallisncrin is a remarkable instance of 

 this. The unisexual flowers are formed under water : 

 the female on long coiled stalks, which at the right period 

 uncoil, and the flower rises just above the surface of the 

 water. .Simultaneously the short-stalked male flowers 

 are detached from the base of the leaf-stalks, and also 

 rise to the surface. .After impregnation has taken place, 

 the st.alk of the female flower coils up again, and draws 

 the seed-vessel down under water, where the seeds ripen. 



It has been explained that heat, moisture, and air are 

 necessary to the germination of seeds, varying immensely 

 for different seeds. We come now to the behaviour of 

 certain seeds under the influence of an unusual or unnatural 

 amount of moisture, heat or cold, especially in relation 

 to the length of the duration of the exposure to any one 

 of these factors. It has been proved beyond dispute, by 

 actual experiment, that the \itality of certain seeds, 

 notably various kinds of bean and convolvulus, is not 

 impaired by immersion in sea-water or rather floating 

 and partially submerged for a period of at least one year ; 

 and that after having been kept quite dry for two or three 

 years. Plants arc actually growing at Kew from seeds 

 treated as described ; and some years ago several seeds 

 of Jiiitadii, cast ashore in the .Azores, whither they had 

 been transported by the (julf .Stream, were raised at 

 Kew. .So far as at present known, all the seeds that will 

 bear very long immersion without injur)- have an in- 

 tensely hard, bony, or cruslaceous coat, that would 

 withstand boiling for a minute or two without killing 

 the embryo. Yet it is diflicult to understand this power 

 of resistance, especially after being kept dry for a long 

 time. This imperviousness to water explains the wide 

 distribution of many sea-side plants, the seeds of which 

 are conveyed by oceanic currents. Mow long such seeds 

 would retain their vitality in water is uncertain, because 

 experiments have not reached the limit. Many readers 

 will rrmember iJarwin's experiments in this connection ; 

 but it shoul<I lie borne in mind that they were chiefly with 

 Mreds of plants not at all likely to be dispersed by the sea. 



It has already been slated that some seeds will 

 bear immersion in boiling water for a short lime, 

 and gardeners occasionally practise this treatment 

 to accelerate the germination of hard-coated seeds. 

 But Heeds of all kinds will bear for a lonsiderably longer 

 pcrio«l a much higher dry temperature than snaking 



Ntt. 13.^1, \nr.. 52I 



in water of the same temperature. It is recorded, 

 by trustworthy authorities, that the seeds of many 

 plants — poppy, parsley, sunflower, and various kinds of 

 grain, for instance- if perfectly dry, do not lose their 

 vitality when subjected to a temperature of 212^ K. 

 for forty-eight hours ; and for shorter periods to a much 

 greater heat. The result in most cases, though not all, is 

 a considerable retardation of germination. Dry grain is 

 equally inipcr\ious to cold. In 1877, seedling wheat was 

 exhibited at the Linnean Society that had been raised at 

 Kew from grain that had been exposed to the intense 

 cold of the .Arctic expedition of 1S74 to 1870. The next 

 question th.it arises is : how long do seeds retain their 

 vitality when stored in the ordinary ways adopted by 

 dealers ? .As a rule, seedsmen and gardeners prefer new 

 seed, because a larger percentage genninates ; and 

 mixing old seeds with new, tells its own talc in irregular 

 gemiination. Nevertheless, there are many seeds that 

 retain their \ itality from five to ten years sufficiently well 

 to be depended ujjon to yield a good cro|3. Old balsam 

 seed, other things being equal, has the reputation ot' 

 yielding a larger iiroportion of double flowers than new : 

 and some gardeners <:onsider that cucumber seed of four 

 or five \ears of age gi\ es better results than the seed 

 of the previous year. .As alread>- mentioned, perfecth- 

 ripened seed will retain its vitality longer than imperfectly 

 ripened seed. In illustration of this, we note that carnu 

 seed grown in France retains its germinati\e power, on 

 the average, longer than Knglish-grown seed, owing to 

 climatal diflVrences. 



There is one other natural condition in relation to the 

 \ itality of seeds that should be mentioned : that is, the 

 duration of the vitality of seeds on the mother plant. 

 Sonie of the .Australian Protcaccir, and some of the fir 

 trees, especially North .American, bear the seed-vessels 

 containing quick seeds of many successive .seasons ; and 

 only under the influence of excessive drought or forest 

 fires do they open and release the seed. Rapid forest 

 fires are often not sufficient to consume the cones, but 

 sufficient to cause them to open and free the seed for a 

 succession of trees. The unopened cones of thirty years 

 have been counted on some fir trees ; and it is avcrri'd 

 that the first seed-vessels of some proteaceous trees do 

 not open to shed their seed, under ordinary conditions, 

 until the death of the parent plant, so that a tree may 

 bear the accumulated seed of half a century or more. 



Finally, a ii^s'i words respecting the txtreine longevilx 

 attributed to certain seeds. The reputed germination of 

 "mummy wheat," from two to three thousand years old. 

 has been the theme of much writing ; but the results of 

 careful subsequent experiments with grain taken from 

 various tombs do not support the doubtless ei|ually 

 conscientious, though less skilfully conducted, expert- 

 ! ments, supposed by some i)crsons to have established the 

 ! fact of wheat of so great an age having germinated. 

 : Indeed it is now known that the expeiitiients mainh 

 ; relied upon to prove this long retention of vitality were 

 falsified by the gardener who had charge of them. 

 .Nevertheless, there is no doubt that some seeds do retain 

 their vitality for a very long period, as is proved b\ 

 numerous well-aulhentii.ited instances, .\lmost everv 

 i writer on physiological botany lites a number of in- 

 stances. Kidney beans taken from the herbarium of 

 Tournefort .ue said to have- germinated after having bieii 

 thus preserved for at least 100 yeais. Wheat and r\e 

 are also credited with having retained their vitality for 

 as long a period. .Seeds of the sensitive plant {AfiiriDtii 

 I piiditii) kept in an ordinary bag at the Jardin des I'lantes. 

 I Paris, germinated freely when sixty years old. .A long 

 I list might be made of seeds that have germinated after 

 being stored for twenty-five to thirty years. If seeds 

 retain their vitality for so long a period as this under 

 such ( onditions. it is t|uite conceivable that seeds buried 

 deep in the earth, beyond atmospheric influences, ami 



