14 COMPENDIUM OF GENERAL BOTANY. 



surface in contact with the thin primordial utricle, thus having the 

 appearance of being in contact with the cell-wall. Among the 

 algae the chlorophyll bodies may assume the form of disks, hands, 

 plates, or even radiate like a star. In the Palm,eUacecB (unicellular 

 algae) the plasmic body, with the exception of the nucleus and hj^alo- 

 plasm, is colored j^reen. Among the Phycochromaceoe (nucleus 

 wanting) there are no differentiated chlorophyll bodies, but the entire 

 plasmic body is homogeneously colored. Spiral chlorophyll bands 

 are seen in Spirogyra (Fig. 3), which also has a nucleus suspended 

 in plasmic threads. A portion of a palisade cell (typical assimilating 

 cell of leaf) with chlorophyll bodies is shown in Fig. 4. 



Origin of Chlorophyll Bodies. — Chlorophyll bodies often result 

 from direct division. When a chlorophyll-bearing algal cell di- 

 vides, each daughter-cell receives a part of the chlorophyll, which 

 part continues to increase by growth or division. Young cells in 

 growing areas (apical areas), as for example in the stems of the higher 

 plants, are supplied with a colorless plasm. It is, however, supposed 

 that these cells contain leucoplastids, that is colorless plasmic 

 bodies which may hecome green on exposure to sunlight. No doubt 

 the unicellular embryo contains besides nuclear substance also leuco- 

 plast substance, and that there is no development de novo of either. 

 Both multiply by division. (Schmitz, Schimper, Meyer.) Under 

 certain conditions leucoplastids maj' be converted into chromoplas- 

 tids, that is non-chlorophyllous coloring bodies. The first of the 

 two important functions (chlorophyll and starch-forming) of leuco- 

 plastids has thus only been touched upon. The leucoplastids are 

 also found in tissues devoid of chlorophyll where starch is formed 

 from pre-existing dissolved products of assimilation, as for example 

 in the potato-tuber. These leucoplastids are called '' starch-builders " 

 (Schimper) because they develop starch-grains ; either on their 

 periphery or within the interior, similar to chloroplastids with the aid 

 of sunlight ; but with the important difference that in 

 the latter case the raw materials are CO, and H^O, 

 while in the case of the starch-builders the starch- 

 grain is formed from dissolved starch, or more gener- 

 ally from assimilated food-substances brought from 

 the green cells. The nature of the starch-builder can 

 be explained best in co!inection with a chlorophyll-grain (Fig. 5, 

 cell 7j). The chlorophyll-bodies are represented as producing starch- 

 bodies on the periphery at c' and within the interior at c" . The 



