Spermatophytes Angiosperms 267 



early, so that the archesporial cell, or even the megaspores, may be 

 seen while the carpel is still as open as in any gymnosperm. 



In the willows, Salix, the bud scales must be removed and the 

 copious hairs should be trimmed off as much as possible with scissors, 

 after which the catkin should be cut in two longitudinally and placed 

 in the fixing agent. 



The cat-tail, Typha, presents a simple type of floral development. 

 The leaves should be dissected away long before the flowers can be 

 seen from the outside. The cylindrical clusters, varying in diameter 

 from 2 or 3 mm. up to the size of one's finger, will afford a complete 

 series of stages. Until the spadix reaches the diameter of a lead 

 pencil, transverse sections are easily cut. For later stages, the outer 

 part of the spadix should be sliced off so that only enough spadix is 

 retained to hold the florets in place. 



Prunus and many other members of the Rosaceae furnish 

 examples of the perigynous type of development. In many of them 

 the floral parts do not occur in the usual succession. 



The epigynous type is well shown in the Compositae. The order 

 of appearance is (1) corolla, (2) stamens, (3) carpels, and (4) calyx 

 (pappus). 



The common dandelion, Taraxacum officinale, affords an excellent 

 series with little labor. Examine vigorous plants which have, as yet, 

 no flowers or buds in sight. Dig up the plant and dissect away the 

 leaves. If there is a white cluster of flower buds, the largest not 

 more than 4 mm. in diameter, cut out the cluster, leaving only 

 enough tissue at the base to hold the buds in place. Larger heads 

 should be cut separately. 



Our most common thistle, Cirsium lanceolatum, shows the floral 

 development with unusual clearness, but the preparation of the 

 material is somewhat tedious. The involucre, which is too hard to 

 cut, must be carefully dissected away. Retain only enough of the 

 receptacle to hold the developing florets in place. A series of sizes 

 with disks varying from 3 mm. to 10 mm. in diameter will show the 

 development from the undifferentiated papilla up to the appearance 

 of the archesporial cell in the nucellus of the ovule. The Canada 

 thistle, Cirsium arvense, is equally good, but it is more difficult to 



