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GARDENERS' CHRONICLE 



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I A Lesson on Plant Physiology and the Plant in j 

 I Relation to Its Environment | 



I Being One of a Series of Lessons of a Home Study Course on Gardening, Appearing Regularly in The Garde.vers' Chronicle | 



I Under the DirecUon of ARTHUR SMITH | 



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ONE of the objects of these lessons has been to set forth the 

 whys and the wherefores of gardening practice to a greater 

 extent than is usually found in ordinary and popular gardening 

 books. In endeavoring to cover as much ground for this purpose 

 as possible each month, it has not been practicable to do more than 

 Tierely scratch the surface of the various subjects dealt with. In spite 

 of lilts shallowness of treatinent and of other shortcomings, it is 

 gratifying to learn from both ainateur and professional gardeners 

 that the lessons have been found interesting. We have therefore 

 decided to delve somewhat deeper into first principles to deal more 

 fully with the various phases of plant life and of the soil upon 

 which that life grows, and we trust that the resulting lessons 

 will prove worthy of continued appreciation. 



The deeper and wider a gardener's knowledge of the underlying 

 principles of his work ; of the whys and the wherefores of his 

 practice, the more interesting it is to him and the more intelli- 

 gently he carries it out. Without at least some knowledge in this 

 direction, he cannot claim to be a gardener at all. .\n important 

 fact to be borne in mind is. that these principles have the same 

 bearing all over the world, and this applies with equal force to all 

 the fundamental operations of gardening, such as soil preparation, 

 fertilizing, seed .sowing, planting, etc. 



To those having only a slight acquaintance with plant life it 

 will be obvious that the grotuid co\ ered liy the above caption can- 

 not be gone over, however shallouly, in one lesson, and, although 

 we are not proposing to deal with it at all e.xhaustively, it is there- 

 fore proposed to 'ake more than one issue in discussing matters 

 included under it. 



.Ml hfc upon the earth is co\ered liy the science of biology, and 

 is divided into two classes or kingdoms : the animal or zoological, 

 and the vegetalile or botanical ; judged by the number of living 

 subjects, the vegetable kingdom is very much the greater. There 

 are some forms of life, principally microscopical, which are 

 claimed by both zoologists and botanists as belonging to their 

 respective branches of science. 



Most jieople are willing lo pay more or less lip service to botany 

 as an interesting subject, but the true relation whicli this branch 

 of sc'ence bears to the daily life of man is appreciated by compara- 

 tively few, and there is a popular impression that botany is of 

 small practical importance, offering as its best reward only the 

 discovery and naming of new plants : to which may be added, 

 soniet me^ much to our ainioyanee, the renaming of old ones. 

 Even many, who know that botany represents the foundation upon 

 which gardening, farniin.g and forestry rest, imagine that its chief 

 aim is the classification of plants. 



There is little in the appearance of linen, su.gar, or rubber, for 

 instance, to remind one of their \ egetable origin ; but when we 

 remember that food, fuel, clothing, lumber, furniture, paper, medi- 

 cines, and hosts of other essential materials are derixed from plants, 

 we get a hint of the universality of the vegetable kingdom, and of 

 the vast importance of the science of botany, especially on its eco- 

 nomic side. 



The raw material required for the Ihings above mentioned is 

 built up by chemical action and stored in one part or another of a 

 plant. Plants are therefore so many laboratories engaged in the 

 manufacture of all kinds of chemical compounds which man has 

 been, and is, slowly, learning to convert to his best use. Through 

 successive centuries these discoveries have been made, first by acci- 

 dent, then by experience, and finally by scientific investigation. The 

 ambition of botanists is to peiietr.ate into the inner recesses of these 

 laboratories of Xature : to di'^cover there her secret processes, and 

 to employ her forces lo carry out their own designs. The vege- 

 table kingdom abounds in problems which need more continual and 

 complete investigation, and questions are contimially arising which 

 scient'sis hesitate lo answer. While we are nowhere at all ap- 

 proaching finality in these connections, still much is known about 

 plant physiolo.gy. 



Literally, physiology means the ■science of Xature. and, although 

 the term is now never used, phytology is the science of plants. 

 .Strictly speaking in present day usage, plant physiology deals w-ith 

 the anatomy of plants and with the funct'ons of their various 

 organs. One of the main features in the art of gardening is to 

 provide such an environment for a plant as w'ill enable all its parts 

 lo function in the highest possible degree. 



The initial starting point of a Ihm-ri-in}; plant's ( botanically 



called phrenoganious ) separate existence is at the time the ovule 

 in the ovary, which is to be found at the lower extremity of the 

 pistil of the dower, matures into a fruit. This becomes fertilized 

 by the pollen produced by the stamens, resulting in the formation 

 of a seed containing an embryo. The ovule stands in exactly the 

 same relationship to the plant as the egg, or ovum, does to the 

 animal, therefore we may say that the starting point of all the 

 higher animals and plants is the egg. 



Among Ho-ivcrlcss plants (known as cryptogamous), that is, 

 plants without either stamens or pistils, such as ferns, mosses, 

 horsetails and fungi, reproduction is by means of spores (simple 

 cells) in place of seeds. These spores are commonly, in the case 

 of ferns especially, contained in one-celled spore-cases (sporangia) 

 and these hold but one kind of minute, one-celled, powdery, numer- 

 ous spores, which are discharged when the sporangia finally split 

 open. 



The lowest forms of plant life consist of a single little sack, or 

 cell. In these, reproduction is entirely by cell-division, that is. a 

 cell divides itself into two or more cells which ultimately separate 

 into single plants. This cell division goes on indefinitely and. 

 when the environnient is favorable, with extreme rapidity. Most 

 of these unicellular plants are microscopic and the micro-organ- 

 isms living in the soil, to which attention has been called in previ- 

 ous lessons, belong to this class of plants. 



.All forms of animal and vegetable life consist of one or more 

 cells. The higher plants and animals are built up of many cells 

 united, which cells assume various forms and properties in the 

 different organs, and, to some extent, in different species. Some- 

 times the united cells can be readily separated from each other, 

 and the cell is then seen to be an independent structure sur- 

 rounded by its own cell-wall. These cells can only be seen through 

 a microscope, although they vary greatly in size, and when living 

 contain a transparent, jelly-like substance, called protoplasm, 

 which protoplasm is the source of, and the medium for the 

 manifestation of, the various phenomena of life. Under certain 

 conditions this protoplasm may become dormant, in which state 

 it may- exist in a dried form for a considerable period, as is the 

 case with seeds, and may again become active under suitable con- 

 ditions of moisture, temperature, etc. 



Growth or increase in size takes place partly by expansion of 

 cells already formed and partly by cell multiplication. The latter 

 may take place by division, as in the case of the unicellular plants, 

 or by the formation of new cells within the older ones, the young 

 cells thus brought into existence attaining full growth by subse- 

 quent enlargement. 



It appears probable that the earliest plant life upon the earth 

 was in the form of unicellular plants, and in the geological period 

 known as the carlioniferous none but flowerless plants existed. 

 Their environment W'as then practically that of a gigantic hot- 

 bed, with the atmosphere in a state of continual mist, thus pro- 

 ducing ideal conditions for these plants to grow with extreme 

 rapidity and to attain a gigantic size. Their reiriains are seen to- 

 day in the deposits of coal which are found close to the X^orth 

 Pole, as well as in other parts of the world. The flowerless 

 plants we have today are the degraded descendants of these 

 earlier forms. The sun's rays could never fully penetrate the 

 continuous pall of mist, and it was not until this environment 

 passed away that flowering plants appeared, these representing a 

 higher and more intricate form of life. 



.As before mentioned, flowering plants are those bearing true 

 flowers ; that is. having stamens and pistils, either both or one 

 or the other, and which produce seeds containing an embryo. 



We may ronglily divide flowering plants into three classes : 

 ( 1 ) Those having perfect flowers ; that is, flowers which all con- 

 tain both stamens and pistils: (2) plants which produce flowers 

 of two kinds on the same plant (monoecious), one of which con- 

 tains the pistils and the other the stamens, and (3") those species 

 having staminatc and pistillate flowers upon different plants 

 (difecious). When the staminate and pistillate flowers are pro- 

 fhiced separately, it is only the latter which can bear fruit. In a 

 few plants, such as the asparagus and the strawberry, some indi- 

 viduals produce perfect and others imperfect flowers. 



Examples of tlie second class can be seen in corn, squash and 

 melon. Sometimes, in the two latter and in their allies, numerous 

 staminate flowers arc iirodnceri. but very few pistillate. It is an 



