252 FINE-STRUCTURE OF PROTOPLASM II 



hydrophobic bias, to form submicroscopic droplets (Fig. 128b). Then 

 they lose their fluorescence, obviously because, owing to their as- 

 sociation, the molecules reciprocally influence each other. Noack 

 (1927) was thus able to show that, contrary to earlier ideas, the chloro- 

 phyll cannot be present in a colloidal state in the plastids. The fluor- 

 escence persists, however, if the chlorophyll is adsorbed in a mono- 

 molecular layer on aluminium hydroxide or globulin. With Noack, 

 therefore, we may conclude that, in the molecular state, the chloro- 

 phyll is present in the plastids as monon?olecular films. Fluorescence is 

 heightened if a monomolecular layer of lecithin is interposed between 

 the chlorophyll and the adsorbant. The assumption must be that this 

 makes the chlorophyll molecules yet more independent of each other 

 so that there is much less mutual interference in their fluorescence. 

 Hubert (1935) devised a scheme by which the molecular morphology 

 of this phenomenon is clarified (Fig. 128c). The hydrophilic pole of the 

 lecithin is orientated with respect to the hydrophilic adsorbant, 

 whereas the hydropobic phytol tail stands parallel to its hydrophobic 

 chains, making the porphin system in Fig. 128 visible in profile. In 

 this state the chlorophyll molecule may best be compared to a signet, 

 the phytol chain being the stem or handle, and the porphin ring the 

 seal. 



As a counter to these established facts, K. P. Meyer (1939) states 

 that his colloidal chlorophyll solutions do fluoresce; but his method 

 of extraction is such that the chlorophyll, instead of being isolated, 

 is dispersed in its natural association with protein and lipids. In at- 

 tempts to produce multimolecular films from chlorophyll, globulin 

 and lecithin, Nicolai and Weurman (1958) obtained non-fluorescing 

 systems of layers. 



The state of the chlorophyll in the living plastids may further be 

 revealed by the position of its absorption bands (Seybold and Egle, 

 1940). For this work the Baas Becking school favoured light ab- 

 sorption in red. Living foliage exhibits an absorption maximum at 

 6810 A (Baas Becking and Koning, 1934; Hubert, 1935). But in 

 chlorophyll isolated from the plant, this absorption band shifts in 

 a varying degree towards the region of the shorter wavelengths. The 

 effect is most marked in hexane, where the displacement amounts to 

 nearly 200 A, for Wakkie (1935) finds the absorption maximum in 

 this solvent at 6620 A. This faces us with the task of seeking states 



