THE MICROSCOPE. 145 



the stems and leaves of plants exposed to light, contained within the 

 so-called " chlorophyll-corpuscles." Sachs describes the grains as 

 appearing inclosed within the chlorophyll grains themselves. The 

 starch-grains are found alone or aggregated at various points in the 

 chlorophyll-corpuscles ; they appear first as bright points which in- 

 crease in size, and becoming more or less spherical at first, may 

 finally be oblate, pyriform, irregular, or angular from crowding. 

 The maternal corpuscles at first increase in size, but subsequently 

 shrink and may finally disappear. The starch grains appear to be 

 formed in some plants irregularly throughout the substance of the 

 corpuscle, but in others they always develop just beneath the free 

 surface, seeming presently to rupture the membrane of the corpus- 

 cle and project beyond. The shape of the corpuscle probably has a 

 determining influence upon the location of the grain or grains. 

 Where it is spherical they appear irregularly over the periphery, but 

 when, as is more common, it is discoid they project around the 

 edge ; six or more may thus girdle the corpuscle, and rarely, minute 

 ones are seen upon the flat surfaces. 



When the starch-grains originate within the corpuscle and 

 remain enclosed, they rarely show signs of differentiation. " When 

 mature they are spherical, completely colorless compound grains con- 

 sisting of hundreds of small similar polyhedral grains," the irregular 

 shape arising from crowding within the chlorophyll-corpuscle: the 

 latter gradually disappears leaving the multiple starch-grain appa- 

 rently a simple sphere, but which when dry breaks up into its 

 elements. Examples of this form of development are found in the 

 four o'clock [niirabilis j'alapa), some species of cactus, [C. specio- 

 cissmus) or some orchids {vanilla planifolia). Starch-grains origi- 

 nating in the second way i. c. upon the periphery, are usually much 

 larger and present more perfect development of hilum and layer, 

 the latter eccentric, the part most developed being that attached to 

 the corpuscle. If the grain is in contact with two or more corpus- 

 cles growth is more marked at each point of contact, proving that 

 tiie corpuscle is the source of nutriment. Examples of this form are 

 found in the stems of the common potato, certain species of Bego- 

 nia, Dieffenbachia, Oxalis, Coctus, etc. 



Parts of plants free from chlorophyll "show that the starch- 

 grains which are in process of development are not surrounded by 

 ordinary protoplasm, but that they are contained in, or attached to, 



