314 



KNOWLEDGE. 



August. 1911. 



vacuole is composed of from two to five smaller ones, in each 

 of which a small starch grain is formed, and as the componnd 

 grain thus formed disappears, the green pigment passes in and 

 thus a chloroplast is formed. 



Meyer and Schimper, on the other hand, concluded that the 

 origin of chromatophores does not take place in the young cell 

 in any of the cases investigated by them, but that all chromat- 

 ophores are derived from other cells in which they previously 

 existed, increasing in number by division. Schimper found 

 chloroplasts in the embrvo-sac and the egg-cell, and concluded 

 that the chloroplasts thus present in the young embryo 

 persist in the ripening seed, but become colourless and lose 

 their function, again becoming green and functional when 

 .germination occurs. 



Bredow made extensive observations on seeds, and found 

 that chloroplasts were always present, though often staining 

 very poorly and being therefore hard to detect. Bredow used 

 chiefly picric acid, which colours all proteid material yellow, 

 but stains plastids more deeply than the other cell contents. 

 He found that the chloroplasts of the seed increase during 

 germination by simple fission, and also by the division of one 

 chloroplast into as many as ten or twelve small ones by 

 numerous irregular divisions. He pointed out that the green- 

 ing of these numerous small bodies led the earlier observers to 

 conclude that the chloroplast originates directly from the 

 protoplasm of the cells of the seedling. 



Famintzin made still more detailed obser\ations on the 

 origin of chloroplasts in seedlings, and especially on the manner 

 in which the chloroplasts, if present in the seed, increa.se by 

 division. Applying various microchemical reagents and stains, 

 and using chiefly thesunflower. Famintzin wasabletodistinguish 

 between the protein grains on one hand, and the chloroplasts 

 and other protoplasmic structures on the other. He found that 

 most of the chloroplasts in the resting seed lie in the film of 

 protoplasm which surrounds each of the protein grains. On 

 placing fresh sections in the light, he observed that these 

 small bodies on the protein grains took on a yellowish colour, 

 and by identifying these bodies in various stages of the seed- 

 ling, he concluded that the sunflower seed contains chloro- 

 plasts. which by simple fission produce those of the seedling. 



The latest investigator of this subject is Miller iBof. 

 Gazette, 1911), who has just published the results of his 

 observations on the sunflower, applying the modern methods 

 of fixing, microtome section- cutting, and staining. Miller 

 confirms the statements of Bredow and Famintzin, who showed 

 that chloroplasts are present in the resting seed and gi\e rise to 

 those of the seedling. Instead of beginning with the young 

 embryo, and working onwards to the seedling, however. Miller 

 has adopted the better method of working back step by step 

 from the seedling to the seed. .According to Miller, the 

 chloroplasts in the early stages are present in the usual posi- 

 tion in the cell, namely, just within the cell wall. He found 

 the numerous small bodies clustered about the protein grains, 

 but he does not agree with Famintzin that these are the 

 chloroplasts. 



.ALG.A.L CO.AL. — The petroleum-yielding coals known as 

 bog-head, cannel, and so on, have been supposed to owe their 

 origin to .Algae. This view, put forward by Renault. Bertrand. 

 Potonie. and other workers in fossil botany, has been some- 

 what widely accepted. The chief evidence of such an origin 

 is the occurrence in these coals, as well as in bituminous 

 schists and oil shales, of abundant spherical or oval bodies, 

 often arranged in layers, these bodies being interpreted as 

 colonial Algae. They have recently been investigated by Jeffrey 

 {Proc. Anier. Acad.. \'ol. XLVL, 19101, who has elaborated 

 a method for obtaining nvnnerous thin sections in series, the 

 result being that the structure, and by inference the nature, of 

 these bodies can be brought out with a clearness not hitherto 

 possible. 



Jeffrey shows that these bodies are certainly not .\lgae, but 

 the spores of Pteridophytes and other fern-like plants, which 

 formed an important part of the Palaeozoic flora and which 

 have always been regarded as largely responsible for the 



formation of ordinary coal. This conclusion destroys the 

 Algal theory of the origin of petroleum and similar substances, 

 and refers such products to the waxy and resinous spores of 

 Pteridophytes, which were laid down on the bottoms of the 

 shallow lakes of the Coal Period. These lacustrine layers, 

 the mother-substance of petroleum, form either cannels, bog- 

 heads, or bituminous shales, according to the proportion of 

 spores and the admixture of earthy matter. Pressure and 

 temperature, either separately or combined, in the presence of 

 permeable strata, have brought about the distillation of 

 petroleum from such deposits. 



ALKALOIDS AS PLANT FOOD.— It has always been 

 supposed that the various alkaloids found in plant tissues are 

 purely waste products, not entering again into metabolism. 

 However, some recent observations by Comere [Bull. Soc. Bot. 

 France, Vol. LVIL. 1910) appear to show that some of the 

 alkaloids can be used as food materials. In fact, Comere 

 finds that some alkaloids can be used by plants as the sole 

 source of nitrogen. He worked with the freshwater Algae 

 i'lotliri.x and Spiro<iyra. The alkaloids used (morphine, 

 atropine, cocaine, quinine, and strychnine) were added 

 gradually as assimilated, so that the plants wei-e never 

 subjected to strong solutions. The plants readily assimilated 

 morphine and atropine, and less readily cocaine. Quinine, 

 however, could not be assimilated, while strychnine proved 

 very poisonous even in great dilution. 



KESFKVF FOOD IN BORDERED PITS.— It has 

 become a commonplace that the most familiar plant repays 

 renewed investigation. A short time ago, it was found that 

 the so-called " scalariform tracheids " of the common male 

 fern and the Bracken, which ha\'e served generations of 

 botanical students as types of the fern alliance for dissection 

 and laboratory work, are in reality true vessels similar to 

 those in the wood of the higher plants. Recently, Lakon 

 [Bcr. ilciitscli. bot. Ges., 1911), has shown that the familiar 

 bordered pits in the tracheids of the common coniferous trees, 

 Scots pine and spruce fir, contain at certain stages numerous 

 starch grains and oil drops, and therefore evidently serve as 

 storehouses of food in addition to their ordinary functions in 

 connection with transport of water. Lakon states that while 

 making observations on the reserve foods in various trees, he 

 noticed starch and oil in the pits of the tracheids. At first he 

 thought that some starch and oil must ha%e simply got into 

 these pits by accident from the parenchyma cells of the 

 medullary rays, in the process of section cutting. However, 

 on making more careful preparations he proved that the starch 

 and oil actually occur in the pits, even where the tracheids are 

 not in contact with parenchyma cells, and he found them in 

 microtome sections of material embedded in paraffin — that is. 

 under circumstances which precluded the possibility of the 

 accidental passage of starch and oil into the tracheids from 

 the other tissues of the wood. 



Having clearly established the fact itself, Lakon proceeds to 

 its explanation. Two alternatives are possible: — (1) the 

 starch and oil may have been left behind in the pits while the 

 tracheid was developing from a living and food-bearing cell; 

 (2) some of the protoplasm of the tracheid-forming cell may 

 have persisted in the pits, the glucose in the cell-sap being 

 later converted into starch and oil. Lakon inclines to the 

 second explanation. He finds that during the winter, when 

 the parenchyma cells of the rays contain only oil, the pits 

 of the tracheids also contain oil and not starch ; and that 

 in spring, when the parenchyma cells contain much starch and 

 little oil, the same change occurs in the pits. Since a change 

 of this kind could hardh' occur in the absence of living 

 protoplasm, it appears probable that such protoplasm is 

 present in the bordered pits, and Lakon was able to demon- 

 strate this in some cases. 



Lakon states that in the literature there is only one recorded 

 case where protoplasm, starch and oil occur in the fully 

 developed conducting tissue elements of vascular plants, 

 namely, in the stem of various species of plantain iPlaiitago). 

 In the conifers investigated by Lakon, the protoplasmic 



