May I, 1889.] 



Garden and Forest. 



213 



that unless new plantations are made they gradually dis- 

 appear. But the plant well repays the trouble and expense of 

 occasional renewal. Some of the early varieties of the single 

 Daffodil {Narcissus Psejtdo-Narcissiis) are already out, in the 

 warmest pockets of the rockery, and show what the family 

 will do after another week or two of warmer suns. The lovely 

 Bloodroot {Sanguinaria) has sent up its one-flowered scapes, 

 and the white star-shaped flowers are just opening in advance 

 of the large heart-shaped and deeply-lobed leaves, which make 

 a fine show all summer long. This is one of the most satis- 

 factory of all our native flowers to bring into the garden. The 

 round-leaved Violet ( Viola rotundifolia) has just opened its 

 yellow flowers here for the first time. It is a rare northern 

 plant, with stem-leaves of the shape indicated by its name, an 

 interesting species to botanists, and one which, should it take 

 kindly to captivity, will prove a good addition to garden plants. 

 The various Hepaticas, double blue, double purple and double 

 white, are in full bloom, as are the less showy, but not less 

 attractive, single varieties. The Hepatica lends itself to 

 doubling better than most flowers, and some of the intensely 

 double, deep-colored sorts are among the most beautiful 

 ol)jects imaginable in the rock-garden in April. 



A few early-blooming shrubs harmonize just now with these 

 humbler plants. The most conspicuous of these is the ever- 

 green Japanese Andromeda {A. Japoiiica), near relative of 

 our Allegheny A. floribiinda, but of looser habit, with broader 

 and looser panicles of handsome white flowers. These 

 are rarely seen to advantage in this climate, as they ap- 

 pear before the cold weather is over, and so are generally 

 destroyed just as they are opening. This year the exception- 

 ally mild winter has favored them, and they are just now in 

 great beauty. Much better, too, this year, than I remember 

 it here is Daphne mezereum its leafless branches being com- 

 pletely smothered with its fragrant rose-colored flowers. It is 

 an excellent hardy shrub, of neat and compact habit. The 

 flowers are always abundant and always early, and they are 

 succeeded by handsome scarlet berries. The Cornelian Cherry, 

 the Corjius ntascula of Europe, i? at its best, too, covered with 

 sheets of golden bloom. It is an admirable hardy shrub or 

 shrub-like tree not too often seen in this country, although it 

 should find a place wherever spring flowers are valued. It 

 never fails to bloom profusely, and is beautiful, too, later in 

 the season, when its ample foliage appears, and when its 

 branches are covered with the scarlet, cherry-like fruit. 



Boston, April i8th. C. 



Principles of Physiological Botany, as Applied to 



Horticulture and Forestr}'. 



XVIII. — Germination. 



''pHE sprouting of the seed is a special example of growth 

 -*■ under favorable conditions. The supply of building ma- 

 terials is of precisely the right kind and of sufficient amount to 

 insure rapid development. Under the head of "Growth" the 

 principal facts have been already considered by us, so that we 

 can now confine ourselves to those features vi^hich are peculiar 

 to the seed itself. 



The food in the seed, whether it exists as oil or as starch, is 

 in a form adapted to preservation. Hence this food remains of 

 good quality long after the vitality of the germ may have been 

 lost. 



The conversion of this solid food into forms which can 

 be utilized by the germ, is effected by one or more of the 

 nitrogenous, inorganic ferments, which we have already exam- 

 ined briefly in a preceding paper. The most important part is 

 played by that which is known as diastase, an enzyme or fer- 

 ment, which changes starch into a substance which readily 

 goes over into the form of sugar. In oily seeds there is 

 apparently a complete change in a good port'ion of the oil, by 

 which starch is produced, and this is then consumed as the 

 food of the germ. In the newer parts of such seeds, and in the 

 paths of transfer, starch can usually be detected by appropriate 

 tests without any difficulty. 



_ In all these changes during germination, there is an absorp- 

 tion of water. Without enough water to insure perfect solu- 

 bility of the solid food, the process of germination goes on 

 only slowly and irregularly. But in point of fact, the amount 

 of water furnished to a seed must (except in the case of 

 aquatics) be so given to it as not to exclude free access of air; 

 that is, the oxygen of the air must have free access to the 

 soaked seed. But, even widi these absolutely necessary con- 

 ditions, the seed will fail to germinate unless another is 

 afforded — namely, a certain temperature. This is very different 

 for different seeds, as might be expected from wha't we have 

 already seen as regards growth in general. A few sorts will 



begin to sprout at the temperature of thawing ice, but for all 

 6i our ordinary plants in general cultivation (except certain 

 members of the Cress family) the temperature must be not far 

 from 60° to 90° Fahrenheit. 



The three conditions are, therefore, water, oxygen and 

 warmth. Can we hasten germination by modifying the favor- 

 able conditions in any way — that is, by making them more 

 favorable ? Various chemical agents have been emploved for 

 this purpose, notably those which can yield to the seeds oxygen 

 in its active form, as ozone, but the experiments have not been 

 practically successful. 



Attention should be called to the interesting fact that some 

 seeds appear to take their own time for beginning to sprout. 

 While many seeds germinate speedily, and whenever favora- 

 ble conditions are present, there are many which do not start 

 until definite periods of rest have elapsed. The seeds of man\- 

 of our forest-trees are of this sort, and in their case it is not dif- 

 ficult to see that the refusal to start at once, even when all the 

 necessary conditions are afforded, has something to do with 

 the protection of the plantlet against beginning its develop- 

 ment at an unpropitious season. It is, in short, a conservatix-e 

 faculty. 



Whether light affects germination to any appreciable extent 

 is a question which has been attacked in an experimental 

 manner, but as yet with inconclusive results. There are some 

 seeds whose sprouting appears to be plainly hindered by ex- 

 posure to bright light, while there are many others which are 

 as plainly indifferent. Much can be learned by an attentive 

 examination of the manner in which seeds are self-sown in 

 nature. Some seeds are scattered by nature on the surface 

 of good soil, and there remain uncovered. Here, on the 

 very surface, they will germinate freely and produce good 

 plants. The practical side of this and allied questions is pre- 

 sented in a trustworthy manner by a competent authority* on 

 the raising of plants from seed in a paper wherein direc- 

 tions are plainly given for treating seeds from the period 

 of their ripening to the time of sowing, and the proper con- 

 ditions are insisted upon in a clear manner. In that interest- 

 ing paper the directions follow almost exactly the teachings 

 of nature, so far, at least, as it would seem possible they could 

 be adapted to the exigencies of tree-planting on a large scale. 



When the germ develops, there is speedily seen a definite 

 assumption of form and direction of parts ; the stem rights 

 itself, and the root descends in search of moisture and mineral 

 matters. At this earliest period of growth the seedling re- 

 quires great care at the hand of the cultivator. Proper con- 

 ditions of light must be afforded, in order that the work of 

 assimilation may be adecjuate to the needs of the young plant; 

 but, on the other hand, care must be taken to avoid exposure 

 to too intense a light under artificial conditions. Other con- 

 ditions, such as temperature, moisture, require the greatest 

 attention. 



The practical solution of these difficult questions must be 

 sought in horticultural and arboricultural treatises, but the 

 underlying principles of successful practice are to be found in 

 the accepted statements of modern physiological botany. 



There are also certain other practical difficulties which follow 

 the cultivator from the moment he places the seed in the soil. 

 The plants under his care are liable to fall a prey to disease. 

 The study of plant-diseases belongs to what is termed vege- 

 table pathology, a subject which can be alluded to here only in 

 the most general terms. We refer to the matter only that our 

 examinations of the functions of healthy plants may be sup- 

 plemented by a glance at the same functions when they are 

 disturbed by disease. Many of these diseases are caused by the 

 invasion of other organisms, which may be collectively termed 

 fungi (including under that term all the so-called microbes or 

 bacteria in the widest sense). The discussion in this journal 

 of these invasions as applied to special cases has been entrusted 

 to one who has made very extensive contributions to many 

 parts of the field, and therefore only tlie briefest general state- 

 ment is necessary at present. 



With respect to attacks of fungi on ripening and germinating 

 seeds, it is merely requisite to say at this point that these fun- 

 gal organisms are unable to exist unless they find food which 

 has been prepared by other organisms. They can take this 

 prepared food, even from the very tissues of the organisms 

 which they attack, destroying not merely the supply of nutri- 

 ment, but the organisms themselves. Reserving for the next 

 paper a fuller treatment of this subject, we may turn for a 

 moment to a consideration of a single question, namely, as to 

 whether it is possible to kill the fungi which invade seeds, 

 without killing the germs of the seeds. Attempts have been 



*The Propagation of Trees and Shrubs from Seed. By Jackson Dawson, of the 

 Arnold Arboretum of Harvard University. 



