METABOLIC PROCESSES IN THE PLANT. 319 



of proteids and fats ; starch is completely absent in the ripe seeds. 

 The still unripe maturing seeds possess, however, much starch. 

 It streams to them from the assimilatory organs of the plant, 

 and is ultimately completely used up for the formation of fat in 

 the seeds. We prepare transverse sections from a green pod of 

 Brassica Napus (I examined, e.g., on May 20th, pods 6-8 cm. in 

 length). Between the two carpels we see the false septum. The 

 fruit tissue itself consists of a strongly cuticularised epidermis, 

 green and colourless ground tissue, and a number of vascular 

 bundles. The young seeds are seated on the united, margins of 

 the carpels. If we treat sections with chloral hydrate and iodised 

 Potassium iodide solution, we find that the tissues of the fruit and 

 seed contain much starch. 



The ripe hypanthium of the pear is, as is known, very rich in 

 sugar. Since the fruit itself contains but little chlorophyll, it 

 follows that at all events most of the material required for its 

 growth, and for the production of the sugar deposited in the 

 hypanthium tissue, must be conveyed to it from elsewhere. The 

 fruit stalk conducts the plastic material. If we prepare trans- 

 verse sections from the fruit stalk of the pear (I made an exami- 

 nation on the 8th of June), the circle of vascular bundles between 

 the cortex and the pith can be at once recognised even under low 

 magnification. The bast part of the vascular bundles has on the 

 outside a thick layer of bast fibres, then immediately follows a 

 layer of cells (the starch sheath) in whose elements we observe 

 Large quantities of starch. In the parenchyma of the hypanthium 

 of the pear, I found on June 8th but little starch ; it was present 

 only in isolated cells, obviously indicating that the starch is very 

 rapidly used up. At a still earlier stage of development (on May 

 2nd) I could detect no starch in the cells, even on treating thin 

 sections of the hypanthium with chloral hydrate and iodised 

 Potassium iodide solution. 



If we cut transverse sections through a flower of Phaseolus 

 after removing the petals and sepals, we shall observe the mono- 

 merous ovary, surrounded by the split filament tube. In Phaseo- 

 lus and many other Papilionacese only nine of the ten stamens 

 are connate, one stamen is free. The ovary bears the ovules on 

 its ventral suture. According to Sachs, 1 the following points in 

 particular are to be observed in the ripening of the fruits and 

 seeds of Phaseolus (P. vulgaris). 



Immediately after shedding the petals, no starch is to be found 



