MOVEMENTS OF CHLOROPHYLL-CORPUSCLES. 



619 



into balls at certain points ; these aggregates thicken as new corpuscles are con- 

 tinually being added, and obstruct the vesicle as they swell up into clumps 

 filling up the whole diameter, all the chlorophyll disappearing from the inter- 

 vening portions. After a few minutes, therefore, the previously uniformly 

 green tube appears to the unaided eye, or under a lens, divided into unequally 

 large and irregularly arranged dark green zones alternating with colourless trans- 

 verse ones.' 



We may now turn to the behaviour of the chlorophyll-corpuscles in ordinary 

 cells united into tissues, and first consider an example where these cells form a 

 single layer only, as in the case of 

 the leaves of the Moss. In ordi- 

 nary diff"use daylight the chloro- 

 phyll-corpuscles in the leaves of 

 the Moss, as well as in the similarly 

 constructed prothallia of Ferns, 

 lie only on the outer surfaces of 

 the cells, the walls which separate 

 any two cells from one another, and 

 which are situated at right angles 

 to these not being furnished with 

 chlorophyll-corpuscles. In Funa- 

 ria (p. 85, Fig. 82), according to 

 Borodin, even a short exposure to 

 darkness suffices to alter this dis- 

 position ; the chlorophyll-corpus- 

 cles abandon the free outer walls 

 of the cells, and travel over on 

 to the side walls, so that after a 

 time the upper and lower sur- 

 faces of such a leaf, and of any 

 one of its cells, are completely 

 deprived of chlorophyll. If the 

 leaves are exposed to the light 

 the previous arrangement very 

 soon re-appears. In the simi- 

 larly one layered parenchyma of 



Lemna irisuka (one of the Duckweeds) the free superficial walls of the cells are 

 likewise found to be furnished with chlorophyll-corpuscles in ordinary daylight ; 

 but if such a plant is exposed to the action of direct sunlight there takes place, 

 as Borodin, found, a rapid alteration in the distribution of the chlorophyll-corpuscles. 

 After 10-15 minutes they cover the side walls evenly, as shown in Fig. 362 B ; 

 seen in plan the chlorophyll-corpuscles form in this condition a regular network, the 

 meshes of which correspond to the individual cells. After exposure to continuous 

 sunshine for some time this is no longer the case ; the corpuscles now form irregular 

 groups, which occupy the angles where several cells are contiguous. Continuance 

 of the illumination results in no further change ; but if the plant is removed 



Fig. 362.— Transverse section of the leaf of Lemna trisidca (after Stahl). 

 A plane position (in daylight), B arrant,'enient of the chlorophyll-corpuscles 

 in intense light, C position in the dark. 



