^6 MORPHOLOGY OF THE CELL. 



completely reconstituted by the union of the matrix with the substance of the aleurone- 

 grains. 



Pfeffer followed out the formation of the crystalloids in Ric'mus and Euphorbia sege- 

 turn; they arise nearly simultaneously with the globoids, at a rather early period, and 

 both grow gradually, while the turbidity of the cell-contents at first somewhat increases. 

 They lie, at an early stage, close to one another, and completely surrounded by the 

 turbid mass; the vacuoles which Gris figures (Recherches sur la germination, PI. I, Figs. 

 10-13) are the result of the disorganisation of the cell-contents. The crystalloids are 

 from the first sharp-edged; and, as soon as their size permits their shape to be 

 recognised, it agrees with the mature form. The envelopment of crystalloid and 

 globoid by an amorphous coating does not begin till the crystalloids are mature and 

 the seed has begun to dry. 



On germination the crystalloids dissolve as well from without as from within, till 

 after the amorphous envelope has first disappeared ; their external membranes for a time 

 persist, but gradually become invisible. The globoids also dissolve (no doubt in conse- 

 quence of the acid reaction which the tissue assumes), and in the case of old seeds from 

 the outside inwards. The aleurone-grains destitute of a crystalloid swell up, and resume, 

 on the germination of the seed, the form which they possessed in ripe but undried 

 seeds ; they begin to mix gradually with the substance of the matrix ; their solution 

 can sometimes be followed from without inwards ; but they often coalesce as mucila- 

 ginous masses. These changes occur with the first signs of germination in the embryo ; 

 formation of starch takes place simultaneously in the contents of the cells. 



Sect. 9. Starch- Grains ^ — Plants which grow under favourable circumstances 

 produce by assimilation a larger quantity of formative organisable substance than 

 they require or can employ at the time for the growth of the cells. These mate- 

 rials are stored up in some form or other in the cells themselves, and only come 

 into use later. It has already been show^n how this takes place with albuminous 

 protoplasm-forming materials and with oily substances. Another substance, in the 

 highest degree organisable, Starch, is formed beforehand and stored up in far larger 

 quantities in anticipation of future use. Starch always appears in an organised 

 form as soHd grains having a concentrically stratified structure, which arise at 

 first as minute dots in the protoplasm, and continue to grow while lying in it ; if, 

 at a subsequent period, they reach . the cell-sap and cease to remain in contact 

 with the protoplasm which nourishes them, their growth ceases ^. Every starch-grain 

 consists of starch, water, and of very small quantities of mineral substances (ash). 

 Starch itself is a carbo-hydrate of the same percentage composition as cellulose, to 

 which it bears the greatest resemblance of all known substances in chemical and 

 morphological properties. Starch, however, occurs in each grain in two modi- 

 fications : — Granulose, more easily soluble, and assuming a beautiful blue colour 

 with iodine in the presence of water, and Farinose, easily soluble, and more resembling 



^ Nageli, Die Staikekorner, in Pflanzenphys. Untersuchungen, Heft II, and Sitzungsber. der k. 

 bayer. Akad. der Wissenschaften, 1863. — Sachs, Handbuch der Exp. Physiol., Leipzig 1865, § 107. 

 The account given here is chiefly derived from Nageli's work. 



2 According to Hofmeister, the starch-grains in the latex of Euphorbia appear to form an 

 exception; nothing however is known about their development; the latex always contains pro- 

 toplasm-forming substances, prottids, which perhaps here also take part in the production of 

 the starch-grains. 



