. A compendium of general botany. Plants. REPRODUCTION. 225 and other relations of the anthers. It need, of course, not be stated that insects perform the act of poUination of plants uncon- sciously. The place w^here they are engaged in securing honey is. Fig. 153.—Cross-sections of an anther. (After Sachs.) also the appropriate place to come in contact witli pollen. The following is from Jordan's communication. 1. Anthers introrse. Nectaries intrastaminal, that is, between the androecium and the gynoecium; as in Dianthus Cartliusiano- rum, Lychnis dioica^ Nymphaea alba^ Comarumpalustra^ Alliu
. A compendium of general botany. Plants. REPRODUCTION. 225 and other relations of the anthers. It need, of course, not be stated that insects perform the act of poUination of plants uncon- sciously. The place w^here they are engaged in securing honey is. Fig. 153.—Cross-sections of an anther. (After Sachs.) also the appropriate place to come in contact witli pollen. The following is from Jordan's communication. 1. Anthers introrse. Nectaries intrastaminal, that is, between the androecium and the gynoecium; as in Dianthus Cartliusiano- rum, Lychnis dioica^ Nymphaea alba^ Comarumpalustra^ Allium Schoenoprasuin, etc. 2. Anthers extrorse. I^ectaries extrastaminal^ that is, be- tween the androecium and the corolla or between corolla and calyx; as in Ranunculus acer, Tilia grandifolia, Parnassia palustrisy etc. Most interesting are those cases in which the anthers appear to be unsuitably related to the nectaries as, for examjjle, in Convolvu- lus arvensis. We cannot take time to discuss these relations. (Compare Fig. 143.) We will now pass from the forms of dehiscence to the mecha- nism of dehiscence. The important factor is the anatomical struc- ture of the anther-wall (Fig. 153, E). The epidermis does not assist materially in the opening of the anther, the librous layer {x) (endothecium) is looked upon as the mechanically active tissue. As has already been stated, the weakest point is where the two valves are attached to the pillar of the connective. Thin-walled cells form the connecting tissue. The question arises. Whence the tension which causes the margins of the valves to separate from the connective? We can actually observe a shortening of the fibrous layer (in the mature anther) during gradual drying, so that the wall curls back. Let us consider the individual cell of the fibrous layer. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1896
