118 



CASSELL'S POPULAIl GAKDENING. 



but had obviously been limited in their growth for 

 want of a supply of available nitrogen. During 

 several months the plants were surrounded by an 

 atmosphere containing abundance of free nitrogen, 

 and the cells in which they grew were penetrated by 

 fluid saturated with that element. The diagrams 

 show that Nos. 4, 5, and 6 formed glumes and palaj 

 for seed when provided with assimilable manure ; 

 but Nos. 1, 2, and 3 barely reached that stage of 

 development, having to depend for their food upon 

 that supplied in the seed sown only. 



Some experiments in seed-germination made at 

 Rothamsted at this period, showed how completely 

 plants are able to appropriate the nitrogen of the seed 

 sown, leaving only traces of nitrates in the soil 

 in which the growth had taken place. Furthei', 

 it has been proved conclusively that potash, phos- 

 phate, or any other manure, provided that it contains 

 no nitrogen, may be supplied to the soil, but all in 

 vain ; little or no increase of crop will be obtained. 

 We thus arrive at the conclusion that plants of 

 all descriptions, whether in the open garden or in 

 the closed conservatory, are unable to make use of 

 the stock of minerals in the soil if there be an in- 

 sufficient supply of available nitrogen. 



It is true that the soil liberates more nitrates than 

 are contained in most garden crops, but being of such 

 a soluble nature, they are very liable to waste before 

 they can be appropriated hy the growing plant ; hence 

 considerable amounts of that substance have been 

 found in the drainage water collected from the 

 experimental fields at Eothamsted. But it is quite 

 certain that healthy plants make great efforts to 

 get hold of all food that is within reach of their 

 roots. Consequently, to be fertile, a soil must be 

 firm enough to afford a proper degree of support to 

 the plants which grow in it, and yet loose enough to 

 allow the delicate fibres of the rootlets to extend 

 themselves in all directions. 



THE LIFE-HISTORY OF PLANTS. 



By Dr. Maxwell T. Masteks, F.E.S. 



REPRODUCTION. 



HITHERTO we have seen the plant feeding, 

 breathing, moving, building. We have seen 

 how within certain limits it may be cut into frag- 

 ments, each of which will, under favourable circum- 

 stances, extend and multiply the parent stock. We 

 were about to write, reproduce it ; but, for the sake 

 of accuracy, we must limit the term " reproduction " 

 to that absolutely new formation which takes place 

 as the result of fertilisation. That new formation is 

 the embryo plant wrapped up in the husk of the ripe 



seed, or nestling within its perisperm. (See ajtte, 

 Vol. I., page 21.) 



In ordinary language, generally too vague for ap- 

 plication to scientific purposes, the seed is looked 

 on as the product of fertilisation, but the seed exists 

 (in a rudimentary state, it is true) prior to that 

 operation. In any case it is the mere casket and 

 food-store in which the embryo plant is packed up. 



A bud is an outgrowth from a parent branch 

 or stem, enabling it to extend in length, or, as we 

 have seen, to multiply it when detached. An embryo 

 is something more than an outgrowth or offset ; 

 it is an entirely new formation, compounded of two 

 elements derived from two distinct sources. Even as 

 every man is a descendant from two parents, so every 

 plant has a similar origin. In a few cases, indeed, 

 the sexes of plants have not hitherto been traced, but 

 their jDresence has now been ascertained in so vast a 

 proportion of the vegetable kingdom that there can 

 be no reasonable doubt of their practically universal 

 occurrence. A general sketch of the mode in which 

 the embryo is formed is then essential for our purpose. 



The conditions under which reproduction and the 

 production of flowers are effected are in some sense 

 the opposite of those requisite for growth. 



The object now is rather to utilise what has been 

 obtained, to change it chemically, and develop it 

 morphologically. It is hence requisite, speaking 

 generally, that the work of accumulation and reserve 

 be over, and that the vegetative growth be checked, 

 so as to allow of the development of the previously 

 formed flower-bud. Presuming that the plant is 

 well developed, and in good health, the supply of 

 food, and especially of water, may be diminished, 

 while, at the same time, a higher temperature is re- 

 quisite than for mere vegetative growth. Many 

 plants grow well enough in this country, but refuse 

 to flower, owing to a deficient amount of heat. But 

 it is here assumed that the flower-buds are already 

 formed in embryo. It is not absolutely proved that 

 a reduced supply of water, greater heat, or the 

 devices practised by the gardener, will positively 

 bring about the formation of flowers where no germ 

 of them pre-existed, though it is probable that this 

 may happen. 



Reduced to its simplest and most elementary stage 

 fertilisation consists merely in the commingling 

 (perhaps the mere contact) of two hitherto separate 

 portions of protoplasm. So far as we can see at 

 present there is no difference in appearance between 

 these two atoms ; nevertheless, the one, stimulant, 

 promotes growth; the other, receptive, grows— 



useless each without the other." 



Fungi and Algae, Mosses and Liverworts we may 

 pass over, not that they are unimportant by any 

 means, but they lie for the most part outside the 



