SPECIAL CASES 593 



must be furnished at the outset with a sufficient store of nutriment to 

 enable the seedlings to form at least one root and one assimilating leaf. 

 Similarly it is by means of their stored reserve-materials that trees form 

 new leaves in spring. Usually more food-material is accumulated in seeds 

 than is necessary for the formation of an independent seedling, and hence 

 unripe seeds may germinate and develop although they contain but little 

 food-material 1 . Similarly when the endosperm of a maize fruit, or the 

 cotyledons of Vicia, PJiaseolns, and Helianthns. are partially removed, the 

 maimed embryo may finally develop to maturity, although when too much 

 is taken away the growing embryo soon dies of starvation 2 . Similar 

 results are obtained when buds or the eyes of potatoes are removed 

 together with small portions of the neighbouring tissues and are allowed to 

 develop. In all such cases the usually slow and feeble growth shows 

 how important a rich supply of food-material is for strong and healthy 

 development, and plants favoured in this manner at the commencement 

 may retain an advantage during the entire summer, and would assuredly 

 suppress weaker plants if free to compete with them. 



As a general rule the reserve-materials of the seed suffice for the 

 development of several leaves, so that the production of plastic products 

 by photosynthesis becomes sufficiently active before the stored food is ex- 

 hausted. Frequently, however, especially in seeds with but little reserve- 

 food, the latter is nearly exhausted at a certain stage of development before 

 photosynthetic assimilation is active, and a retardation of growth ensues. 

 No such transitory starvation occurs normally during the development of 

 shoots from trees, bulbs or tubers, and trees contain sufficient food to 

 form a second crop of leaves after the first has been removed. Similarly 

 potatoes contain a large quantity of food-material after the sub-aerial 

 shoots have been formed, and this food is transferred to the young develop- 

 ing tubers 3 . 



The different food-materials of the seed are not always present in 

 corresponding amounts, but instead the percentage composition may alter 

 as development progresses, and if all supplies from without are cut off 

 large quantities of certain substances may be left untouched. Thus the 



1 See Nobbe, Samenkunde, 1876, p. 339 ; also Sagot, Bot. Jahresb., 1874, p. 831. [Many grass 

 seeds, however, contain barely sufficient food-materials for germination, and hence the young seedlings 

 rapidly perish in darkness or when sown at some depth.] 



2 Such researches were performed by Malpighi, Opera omnia, 1687, I, p. 109, and Opera 

 posthuma, 1698, p. 86. Cf. also Treviranus, Physiol., 1838, Bd. n, p. 594. More recent researches : 

 Sachs, Keimung d. Schminkbohne (Sitzungsb. d. \Vien. Akad., 1859, Bd. xxxvii, p. 84, and Bot. 

 Zeitung, 1862, p. 148) ; van Tieghem, Ann. d. sci. nat., 1873, v. ser., T. xvti, p. 206 ; Blocisrewski, 

 Landw. Jahrb., 1876, Bd. vr, p. 146 ; G. Haberlandt, Die Schutzeinrichtungen d. Keimpflanze, 1877, 

 p. 28 ; Brown und Morris, Bot. Zeitung, 1892, p. 462 (see also Journ. Chem. Soc. for 1892) ; Mesnard, 

 Ann. d. sci. nnt., 1893, vii. ser., T. xvm, p. 296; Hansteen, Flora, Erg.-bd., pp. 428, &c. ; Ewart, 

 Journ. of Linn. Soc., Vol. xxxi, 1896, p. 560 ^Influence upon development of power of photosynthesis), 



3 De Vries, Landw. Jahrb., 1877. Bd. vi, p. 510. 



PFEFFER Q q 



