261(5 Journal of Applied Microscopy 



Sporophyte. 



1. Sketch the entire plant. Note the dichotomous branching, the alter- 

 nating zones of sporophylls and sterile leaves, and the dichtomous roots. 



2. Draw a branch, showing very carefully the tip and several zones of sporo- 

 phylls below. Note that the formation of sporophylls does not stop the growth 

 of the axis on which they are produced. Which are the larger, sporophylls or 

 sterile leaves ? 



3. Draw a single sporophyll with sporangium under low power. 



4. Under high power draw several nonsexual spores. 



5. From alcoholic material cut cross sections of the stem, mount, and draw 

 under low power. Note the epidermis with cuticle, the wide cortical layer, the 

 vascular bundles of the leaf traces, the bundle sheath or endodermis, and the 

 central cylindrical mass of vascular tissue. Inside of the endodermis are a 

 number of more or less parallel strands of xylem and phloem. These structures 

 will be more prominent after staining with iodin solution. 



6. Cut radial longitudinal sections of the stem and compare in detail with 

 the cross section. 



7. Vegetative propagation. Notice the peculiar bulb-like brood-buds near 

 the tips of some branches. Pick off one and draw under dissecting microscope. 



LXIV. Lycopodium obsciinim L. Ground-pine. 



Lycopodium obscurum grows in moist woods, forming long slender rhizomes 

 which creep under the surface of the ground or under leaf mould. From this 

 rhizome upright, aerial branches develop. 



Sporophyte. 



1. Sketch an entire plant showing the rhizome and upright branch bearing 

 a number of cones. 



*J. Draw a single cone under dissecting microscope. Note the spiral 

 arrangement of the specialized sporophylls, and that by the development of a 

 cone the further development of the axis is stopped. What is the probable 

 reason for this? 



3. Under low power draw a single sporophyll showing the sporangium. 

 Note the advance in specialization of this sporophyll over that of the preceding 

 plant. 



4. Under high power draw some of the nonsexual spores ; also some of the 

 spore tetrads from younger sporangia. 



5. Note. — This cone represents a primitive flower. Compare it with the 

 zone of sporophylls in the preceding species. 



LXV. (a) F.quisetum arvense L. Field Horsetail. 



Class and order, Equisetales. Family, Equisetaceae. 



The field horsetail is common along roadsides and railways, on river banks 

 and steep slopes facing the north. The fertile branches come up in April and 

 May, while the sterile ones begin to appear at about the same time, but do not 

 reach their full development until later in the season. Spores may be collected 



