ig6 



SCIENCE-GOSSIP. 



years and even beyond. The above remarks apply 

 to fruits of Cevatophyllum never allowed to dry, but, 

 curiously enough, of fruits dried two or three 

 months eighty per cent, germinated in the first 

 year. 



No very definite results have as yet been yielded 

 by my experiments on the influence of light and 

 shade on germination. Hitherto, however, it has 

 occurred in bright diffused light and in moderate 

 shade, but not in darkness. It may be here 

 observed, in passing, that the seeds of river or 

 pond plants behave very differently in this respect. 

 For instance, under the same conditions of tem- 

 perature, some, like those of Callitriche aquatica, 

 do not germinate in darkness ; others, like those of 

 Ivis pseudacovus, germinate much more readily in 

 darkness than in the light, whilst those of Myvi- 

 ophyllum seem to be indifferent to either light or 

 shade. With respect to the temperature needed 

 for germination the following results were obtained. 

 In my list of nearly a hundred of our aquatic and 

 land plants arranged in the order of their germina- 

 tion in water, between the beginning of January and 

 the end of April, Cevatophyllum demersum, Hydrocotyle 

 vulgaris and Iris pseudacorus, occur at the bottom of 

 the series. This itself is suggestive of a high 

 temperature, and from my experiments I place the 

 initial temperature at sixty-two degrees Fahr., 

 which is the mean water-temperature of the week 

 prior to the germination of ten per cent, of the 

 seeds of Cevatophyllum. Adapting this estimate to 

 the thermal regime of our ponds and rivers, we 

 should not generally expect to record this tempera- 

 ture in the Thames until the middle of May ; but 

 in the shallows of ponds, where this plant chiefly 

 fruits, it would be observed two or three weeks 

 earlier, namely, at the end of April. 



The embryo has attracted the attention of so 

 many eminent botanists that I cannot do better 

 than refer the student to " Baillon's Natural History 

 of Plants " for one of the most recent authoritative 

 statements of the subject. It is there described as 

 a complete plant in miniature, a description best 

 adapted to explain its puzzling characters. I pass 

 on, therefore, to the germination. This was long 

 ago described by Schleiden (Linnaea, xii, p. 345), and 

 though it is not easy to supplement his clear 

 account of the process, his figures by no means do 

 justice to his observations. I have endeavoured to 

 illustrate an advanced stage of germination in fig. a. 

 If the fruit is turned round, it will be perceived 

 that it has split along its borders into two halves 

 -which are still kept in position by the style. The 

 cast-off case retains the two halves in their place, 

 and by means of the presence or absence of the 

 slits the geologist could determine whether or not 

 the fossil fruits of the Norfolk Forest Bed had ever 

 germinated. No growth of the radicle accompanies 

 the germinating process. The liberated embryo, a 



white helpless-looking little object, remains at the 

 bottom (see fig. b). In a couple of days the large 

 fleshy cotyledons will have begun to separate (fig. c), 

 and at the end of the week their size will have much 

 increased, whilst with the distinct development of 

 the first internode the first pair of leaves will be 

 readily distinguished (fig. d). They are linear and 

 subulate in form, but not forked, and decussate with 

 the cotyledons. These leaves, which arise from the 

 base of the stem, have been the subject of much 

 discussion amongst botanists, the point at issue 

 being their relation to the cotyledons. This matter 

 cannot be treated here ; but it may be remarked 

 that whilst Brongniart (Ann. des. Sc. Nat., Series I, 

 tome xii, p. 251) was undecided whether the fleshy 

 lobes were cotyledons or merely appendages of the 

 radicle, De Candolle, in his " Prodromus " (iii, p. 73), 

 refers to the embryo as having four whorled 

 cotyledons. 



With the differentiation of the lowest whorl of 

 leaves as*-the axis lengthens, it will be found to be 

 composed of four leaves, all of them usually like 

 those of the first pair, but occasionally two of 

 them are singly forked. Then follows a whorl of 

 eight leaves, of which four are undivided and the 

 rest forked. The succeeding whorl has all its 

 leaves divided. When nearly three inches long, 

 the seedling rises to the surface and floats horizon- 

 tally, the cotyledons being persistent and healthy 

 even in plants many weeks old. Seedlings always 

 kept in deep shade develop the stem very slowly, 

 whilst the cotyledons and first pair of leaves 

 lengthen considerably, the last looking like a pair 

 of roots (fig. e). A curious feature in the history 

 of the seedling is that the radicle undergoes but 

 little change, whilst no roots are produced. This 

 long since attracted the notice of Schleiden, who 

 found that his young plants, eleven inches long, 

 neither displayed any alteration in the radicle nor 

 produced roots. He therefore characterised the 

 species as a planta libera that never attached itself 

 by roots to the bottom (Linnsea xii, p. 345). He had 

 been before surprised at not meeting with any 

 reference to the roots in descriptions of the plant, 

 and he had never observed them in the large 

 number of individuals that had passed through his 

 hands. My experience has been the same, and 

 when we turn to the works of Baillon, Syme, and 

 similar botanical authorities, they are silent on this 

 matter. With the object of further testing the 

 ability of the plant to produce roots, I placed a 

 germinating fruit under the mud at the bottom of 

 a vessel of water, whilst other fruits in the same 

 condition were placed on the mud. The seedlings 

 developed from the uncovered fruits made no 

 attempt to show roots, nor did they endeavour in 

 any way to strike into the mud, and in due time 

 they floated up. In the case of the fruit buried 

 under the mud, the seedling subsequently pushed 



