50 MORPHOLOGY OF THE CELL. 



Nageli. They are usually colourless, but sometimes act as vehicles of colouring 

 matters (not green) which may be removed from them. Their collective mass 

 shows all the essential reactions of protoplasm, its power of coagulation and of 

 taking up colouring matters, the yellow reaction with potash after treatment by nitric 

 acid, as well as that with iodine. The solubility of different crystalloids varies 

 greatly, as is generally the case with albuminoids. They are capable of imbibing 

 water, and swell up enormously under the influence of certain solutions ; their outer 

 layer possesses greater power of resistance than the inner more watery mass. Those 

 crystalloids which have been most carefully examined consist of a mixture of two 

 kinds of materials of different solubility ; the two are so combined that when the more 

 soluble is slowly removed, the less soluble remains as a skeleton (Nageli). 



Their form is very different in different plants; they appear as cubes, tetra- 

 hedra, octohedra, rhombohedra, and in other forms ; usually, however, their crystallo- 

 graphic characters cannot be exactly defined, a consequence of their small size and 

 of the inconstancy of their angles. 



In quickly growing organs of phanerogamic plants they are known only in 

 Lathrcea squamaria ; more commonly they form in cells where large quantities 

 of reserve-materials are collected which are only turned to use at a later period; 

 the crystalloids themselves appear to be a form of protoplasmic structure especially 

 adapted for a dormant condition (as potato-tubers, many oily seeds) ; they are seldom 

 found in cells which contain sap (potato-tubers), more often in sapless, and especially 

 in oily seeds. Crystalloids containing colouring matters are found in the petals 

 and fruits. Sometimes they are formed only after the action of alcohol or a 

 solution of sodium-chloride on the plants externally or internally (Rhodospermine). 



The crystalloids of potato-tubers are imbedded in the protoplasm ; those that 

 are widely distributed in the tissues of LathrcBa squamaria are contained in great 

 numbers in the interior of the nucleus; those found in oily seeds are generally 

 enclosed in grains of aleurone. 



The Crystalloids discovered by Cohn in the tubers of the potato are convenient for 

 observation ; they are found very abundantly in some kinds, in others less frequently, 

 in the parenchyma- cells beneath the skin which contain but little starch, but tolerably 

 deep in the tissue ; they lie enclosed in the protoplasm. Generally they are in the form 

 of cubes (less often of derivative forms, as tetrahedra) of the most perfect form. 

 Those found by Radlkofer in the nuclei of LathrcBa squamaria lie together in great 

 quantities within each nucleus ; they have the form of thin square rectangular plates ; 

 sometimes they appear to have rhombic or trapezoid forms ; Radlkofer thinks it most 

 probable that they belong to the rhombic system. These crystalloids present themselves 

 immediately to observation, and their relation to their environment is at once clear. 

 The case is different with the crystalloids of oily seeds enclosed in grains of aleurone ; 

 I shall recur to their properties, and will only mention here that the crystalloids of the 

 brazil-nut are obtained in quantity by washing out the crushed oily parenchyma by oil 

 or ether, the crystalloids settling down in the form of fine meal ; in sections through 

 the tissue but little can be clearly made out. They were carefully investigated in 

 the isolated state by Nageli; according to the manner in which they are seen they 

 appear rhombohedral, octohedral, or tabular ; but it is uncertain whether they belong 

 to the hexagonal or the klino-rhombic system. Dry crystalloids placed in water alter 

 their angles about 2° or 3° ; in solution of potash they swell strongly and then alter their 

 angles 15° or 16°. By weak acids and dilute glycerine a substance is extracted, and a 



