SPECIAL CASES 



595 



separate out as amorphous masses or as regular crystalloids (Sect. 78). In 

 the form of insoluble or colloid bodies very marked accumulation is 

 possible without a dangerously high osmotic pressure being produced 

 (Sect. 24). The condensation of monosaccharides to polysaccharides is of 

 similar importance, although in certain cases, as for example in the onion, 

 glucose may accumulate to a marked extent without undergoing any con- 

 densation, and without any conversion into non-diosmosing carbohydrates 

 being necessary. In organs which are normally subject to desiccation only 

 small quantities of soluble crystalloids appear to be present, and this may 

 be of importance in avoiding the injurious effect of over-concentration during 

 drying. Seeds are organs of this character, and usually contain in addition 

 to proteids mainly starch or oil, or both together. Fatty oil seems in general 

 to be preferable, for according to Nageli l nine-tenths of all Phanerogams 

 possess oily seeds. The oil fills up the spaces between the aleurone grains, 

 which may contain crystalline or amorphous masses of proteid, and in 

 addition globoids composed of an organic compound of magnesium and 

 calcium rich in phosphoric acid. 



Fatty oils are very widely distributed and may even be deposited in 

 succulent organs,, such as the tubers of Cyperns escnlentns, but the prefer- 

 able employment of oil as reserve-material in seeds, spores, &c. must be 

 due to its possessing some special advantages. It is possible that the 

 presence of oil increases the power of resistance to desiccation 2 , while a fact of 

 the utmost importance is that in the form of oil a greater supply of energy 

 can be stored up in a certain space than in the form of carbohydrates. 

 Hence for this reason alone oil is preferable wherever economy of storage 

 is necessary, or when seeds or spores disseminated by the wind require 

 to be as light as possible. 



In all phenomena of this kind many factors enter into play, and 

 when we consider that different food-substances may mutually replace one 

 another in the various organs of the same plant, it is obviously erroneous 

 to conclude from any of the facts mentioned that a substance such as oil 

 affords under all conditions the most suitable nutrient or reserve-material. 

 Development may be either slow or rapid no matter whether the organic 

 food is supplied in the form of sugar, starch, oil or reserve-cellulose, and 

 as a matter of fact a supply of nutriment simply renders possible the 



1 Die Starkekorner, 1858, p. 536. Globoid : Pfeffer, Jahrb. f. wiss. Eot., 1872, Bel. vnr, p. 429. 

 Aleurone grains : cf. Sect. 79. Phosphoric acid : Sect. 74. On other crystalloids, cf. Zimmermann, 

 Beitr. z. Morph. u. Physiol., 1893, p. 54. 



2 [Organs containing oil do not appear on this account to be more resistant to desiccation : thus 

 Dicranum (moss), rich in oil is less resistant than Orthotriclnim or Bryum (Assiin. Inhib., Journ. 

 of Linn. Soc., 1896, xxxi, p. 368), hemp and willow seeds (oily), haricots, kidney beans, &c. 

 (starchy), are readily killed by desiccation, whereas peas, barley (starchy), and linseed (oily) are 

 extremely resistant, and the seeds of Helianthus and Cucurbita occupy an intermediate position (cf. 

 Ewart, Trans, of Liverpool Biol. Soc., Vol. via, 1894, p. 207, and Vol. xi, 1897).] 



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