422 . H. V. Mohl on the Structure of Chlorophyll. 



that they can only be recognized as such by the help of iodine 

 after they have been expanded by boiling), the chlorophyll- glo- 

 bules approach nearer to the above- described first variety, de- 

 void of starch, while on the contrary, others in which the starch- 

 grains are larger form the transition to the above-described 

 globules of Ceratophyllum. These intermediate forms behave 

 differently with water, being sometimes wholly insensible to it 

 (as for instance, the chlorophyll-globules of Vallisneria, Potamo- 

 geton crispus, and the central substance of the leaf of Hoya car- 

 nosa), sometimes swelling out into vesicles in water {e. g. those 

 contained in the leaf of Bromelia Ananas), under which circum- 

 stances the not infrequent isolated starch-grains lie free in the 

 water filling the vacuoles, and exhibit molecular motion. 



With regard to the distribution of the two forms of chlo- 

 rophyll in different cells of the same plant, a general rule exists; 

 In the outer layers of cells, both of bark and of the two faces of 

 leaves, occur globules containing no starch, or others with 

 starch-grains only of exceedingly small size, and ordinarily, like 

 the former, swelling up vesicularly in water. In the layers of 

 the bark bordering on the wood, and in the middle layers o£ 

 leaves, on the other hand, occur globules possessing compara- 

 tively large starch-grains, better resisting the action of water. 

 However, we do not find both kinds of globule in every leaf; 

 there are plants in which all the layers of the leaf, even the 

 middle, contain only chlorophyll-globules without starch. It 

 will not be superfluous to name certain plants in which the 

 diversities just noticed may be recognized. 



Chlorophyll-globules without starch occur in all the layers of 

 the leaves of Elymus arenarius, Iris germanica, Scilla maritima, 

 Tulipa Gesneriana, Phormium tenax, Yucca gloriosa, Clivia nobilis, 

 Menyanthes trifoliata, Ilex Aquifoliunij Aralia trifoliata, Sedum 

 Telephiunij Cochlearia officinalis. 



Leaves where the outer layers contain chlorophyll-globules 

 without starch, while in those forming the middle substance of 

 the leaf, starch occurs, are found in Acrostichum alcicorne, Sira- 

 tiotes abides, Potamogeton crispus, Piper magnoliafolium, Camellia 

 japonica. 



Leaves in which all the chlorophyll-globules contain starch, 

 where however those in the outer layers of cells approximate to 

 those devoid of starch, while those situated in the middle of the 

 leaf contain large starch-grains, occur in Billbergia zehrina, Bro- 

 melia Ananas, Vallisneria spiralis, Viscum album, Ceratophyllum 

 demersum, Hoya car nosa. 



In regard to the preceding enumeration, it must be observed 

 that the statement, w^hether the starch exists or not in the chlo- 

 rophyll-globules, refers only to the fully-developed leaf, and not to 



