CRYSTALLOIDS. 49 



Phaseolus, buds of the tubers of Helianthus tuberosus, &c.) a definitely formed hyaline 

 protoplasm devoid of granules is to be observed, close to the cell-wall, which, as it 

 developes, forms the grains of chlorophyll ; here the appearance is sometimes pre- 

 sented as if the mass were cut up into polyhedral pieces. The formation of the grains 

 of chlorophyll is not always contemporaneous with that of its colouring matter ; they 

 may be at first colourless (as in Vaucheria or Bryopsis, according to Hofmeister) or 

 yellow (in the case of leaves of Monocotyledons or Dicotyledons imperfectly exposed to 

 light, or in the process of development), and may afterwards become green ; in the 

 cotyledons of Coniferae the green colour appears contemporaneously with their origin 

 even in the dark when the temperature is sufficiently high, as also in Ferns. The 

 grains of chlorophyll, after assuming their green colour, grow by intussusception to many 

 times their original size ; if they are parietal, their growth in length and breadth is gene- 

 rally proportional to that of the corresponding piece of the cell-wall and of the proto- 

 plasm-body in which they lie. But if the growth of the cell is very considerable, the 

 growing parietal chlorophyll-grains divide ; this occurs by bipartition, a constriction 

 arising which always penetrates more deeply in a direction vertical to the longest 

 diameter, until the grain at length breaks up into two usually equal secondary grains. 

 If it contained small grains of starch before the division, these arrange themselves round 

 the centres of the newly formed grains. These processes are inferred from the increase 

 of the number of grains on the one hand, and from the frequent occurrence of biscuit- 

 shaped constricted forms on the other hand. After this bipartition of the chlorophyll- 

 grains had been discovered by Niigeli in Nitella, Bryopsis, Valonia, and in prothallia, it 

 was subsequently noticed in all the families of Cryptogams which form chlorophyll ; 

 among Phanerogams also it appears widely distributed ; it was discovered by Sanio in 

 Peperomia and Ficaria, subsequently by Kny in Ceratophyllum, Myriophyllum, Elodea, 

 Utricularia, Sambucus, Impatiens, &c. In cells of the prothallium of Osmunda exposed 

 to feeble light and containing but little chlorophyll, Kny states that moniliform rows 

 of chlorophyll-grains arise by repeated bipartition, which, like the chains of cells of 

 Nostoc, continue to elongate by intercalary divisions ; a branching of the rows takes 

 place here also, in a manner similar to that which occurs in Nostoc ; single grains of 

 chlorophyll increase' in size transversely, and produce branch-rows by division. 



(c) With reference to the Internal Structure of the chlorophyll-bodies, scarcely 

 anything else can be said than that their outer layer often appears denser, and that 

 the proportion of water in the substance increases towards the interior the cohesion 

 decreasing, as is apparent from the formation of vacuoli. A perceptible differentiation 

 into lamellae of different density crossing one another has, at present, only been once 

 observed in old chlorophyll-grains of Bryopsis plumosa (Rosanoff). 



Sect. 7. Cry stalloids \ — A portion of the protoplasmic substance of the cells 

 sometimes assumes crystalline forms ; bodies are formed which, bounded by plane 

 surfaces and sharp edges and angles, possess an illusory resemblance to true 

 crystals, even in their behaviour to polarised hght; on the other hand they are 

 essentially distinguished from them by the action of external agents, and at the 

 same time present significant resemblances to organised parts of cells. It is 

 therefore legitimate to distinguish them by the term Crystalloids proposed by 



^ Hartig, Bot. Zeitg. p. 262, 1856. — Radlkofer, Ueber die Krystalle proteinartiger Korper 

 pflanzlichen und thierischen Ursprungs, Leipzig 1859. — Maschke, Bot. Zeitg. p. 409, 1859. — Cohn, 

 Ueber Proteinkrystalle in den Kartoffeln, in the thirty-seventh Jahresbericht der Schlesischen Gesell- 

 schaft fur vaterliind. Cultur, 1858, Breslau — N.'igeli, Sitzungsberichte der k. bayer. Akademie der 

 Wissenschaften, p. 283, 1862. — Cramer, Das Rhodospermin (in the seventh volume of the Viertel- 

 jahrsschrift der naturfoisch. Gesellschaft in Ziirich). — J. Klein, Flora, No. 11, 1871. 



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