56 



(termed by him porous cells), in the cells of the epidermis of 

 Aspidium exaltatum, of Calla athiopica, in the diachyma of 

 Abies pectinata, Pinus alba. Camellia japonica, &c., and I have 

 observed them in the elementary organs of the medullary 

 sheath and in the cells of the medullary rays of various trees 

 and climbers*. 



A second variety of chlorophylle globule, immediately con- 

 nected with the form just described, possesses, says M. Mohl, 

 sharply defined outlines in common with the preceding, but 

 is distinguished from it by each chlorophylle grain containing 

 several amylum granules. The envelope of these granules 

 appears sometimes smooth-edged and sometimes crenulate 

 when it adheres to the circumference of the individual amy- 

 lum granules. Similar grains are met with in the diachyma 

 of Aspidium exaltatum, Sempervivum tectorum, and in the 

 cells of the pith of Stapelia maculosa, &c. 



Another form of the chlorophylle grain incloses several, 

 but very minute globules of amylum, the blue colour of which 

 on their combination with iodine is not easily perceived, the 

 embrowned coating of the chlorophylle being too thick. Such 

 chlorophylle grains are found, says M. Mohl, between those of 

 the former form passing into them through several interme- 

 diate stages, for instance, in the leaf-petioles of Pothos lanceo- 

 lata, and sometimes in other cellular layers, as in Orontium 

 japonicum, Sedum anglicum, &c. 



The latter form constitutes those which are generally rather 

 large, but less sharply defined than those described : under a 

 high magnifying power a number of very minute particles 

 may be discerned in them, which are coloured by iodine of a 

 deep brownish-yellow. Nevertheless, M. Mohl thinks that 

 these minute granules also consist of amylum, in which opi- 

 nion however I cannot agree ; for after previous extraction of 

 the chlorophylle with aether a yellowish white mass remains, 

 which is coloured brown by iodine, and the cellular sap glo- 

 bules coloured by chlorophylle occur in most plants in this 

 form. 



M. Mohl now starts the question, whether the amylum gra- 

 nules are formed first and the coating subsequently deposited 

 around them, or whether the chlorophylle is first formed and 

 * Physiologic, i. p. 372, &c. 



