The term vascular cryptogam is so old, that you probably won't find it in your text book. It is a collective term for plants that have vascular tissue (this excludes the bryophytes) and which do not have large reproductive units such as the seed. Today we find these plants separated into four Divisions: Psilophyta, Sphenophyta, Lycophyta, and Pterophyta.
Tools: needles, slides & cover slips
Psilophyta
There are only two extant genera in the Psilophyta, Psilotum of Indonesia and Tmesipteris from New Zealand. Psilotum is the common General Botany representative because it is easy to keep and has the most primitive appearance. It has a leafless, photosynthetic, sporophyte with stem borne sporangia. The sections will show you the stele, or vascular system and the inside of the sporangium with its nutritive layer, the tapetum, and simple meiospores. The gametophytes are rare; most botanists have never seen one.
In the greenhouse, you had the opportunity to see living Tmesipteris. The plants are still small and the greenhouse staff is struggling to keep them alive. If they succeed, it will be a rare and notable event.
KEY WORDS: rhizome, synangium, xylem, phloem, endodermis, epidermis, stomate, tapetum.
Sphenophyta
The genus Equisetum is the only remnant of an important division of plants, now mostly found as fossils. We will see local species by the roadside, soon and in the "swamp" by Science B. Others are found in the greenhouse.
Again, we see a photosynthetic sporophyte. Some species have dimorphism of the stem producing separate photosynthetic stems and reproductive stems. The reproductive organ is a distinctive strobilus.
Sections of the stem and strobilus will show the ventilation system of canals and the unusual sporangiophores. Remember to check the distinction between branches and leaves.
There are slides of the gametophytes. It is easy to find antheridia, but archegonia are harder to detect. Don't panic if you don't find one.
KEY WORDS: roots, microphylls, carina, vallecula, central canal, carinal canals, vallecular canals, sporangiophore, strobilus, pseudoelaters.
Lycophyta
Three genera comprise the Lycophyta: Lycopodium, Selaginella, and Isoetes. The quillwort, Isoetes, is seldom studied because it is aquatic and uncommon. We will see it in the greenhouse.
The sporophyte of Lycopodium is a green, prostrate form with microphylls and a distinctive strobilus composed of sporophylls, leaves bearing sporangia.
Our local Selaginella is a common epiphyte on trees, often mistaken for a moss, by the uninitiated. It grows as a weed in the greenhouse along with several exotic species that look like miniature trees. Its strobili are less distinctive, but interesting. They bear two kinds of sporangia, one with large meiospores, megaspores, and one with small meiospores, microspores. Meiospores develop directly into a small gametophytes within the spore wall. The large spores produce female gametophytes, megagametophytes, the smaller produce microgametophytes, males. This is our first acquaintance with heterospory.
KEY WORDS: megasporangium, megaspores, microsporangium, microspores, megagametophyte, microgametophyte, ligule, sporophylls.
Pterophyta
The ferns are largest and most abundant of the vascular cryptogams. The large leaf is a distinguishing character of the ferns. It has several vascular traces that branch in the lamina of the frond. Such a leaf is called a megaphyll. If the leaf bears clusters of sporangia, called sori, it can also be called a sporophyll. Examine the leaf slide to see the sporangia and the indusium. Watch the spore release mechanism of the terrestrial fern under your dissecting scope.
Some ferns exhibit leaf dimorphism, with distinctly different vegetative leaves and sporophylls. Terrestrial ferns are generally homosporous; aquatic ferns are frequently heterosporous. We will examine both.
Thalloid fern gametophytes are photosynthetic and often difficult to tell from hornworts. The gametophytes on our slides are homothallic, or bisexual. They are not self fertile because the antheridia develop first and are exhausted by the time the archegonia are developed. Be certain to see live gametophytes in the green house.
Your instructor will demonstrate the operation of the unusual spore release mechanism of the aquatic fern, Marsilea.
KEY WORDS: sorus, indusium, receptacle, annulus, antheridium, archegonium, venter, neck, canal cells, cover cells, sorocarp, megaphyll.