Question

Which of the following order is not included in Stachyospermae?

• A. Cordaitales
• B. Ginkgoales
• C. Cycadales
• D. Coniferales

Hint:

To remember this classification, break down the names:

\textbf{Stachyospermae} = Stachys (Stem/Axis) + Sperma (Seed) \(\rightarrow\) Seeds on stems. (Think of conifers, Ginkgo).
\textbf{Phyllospermae} = Phyllo (Leaf) + Sperma (Seed) \(\rightarrow\) Seeds on leaves. (Think of cycads and seed ferns).

Answer 1

The Correct Option is C

Step 1: Concept Overview:
This question pertains to an older gymnosperm classification system, developed by botanists like Sahni, that categorized gymnosperms based on ovule position into two main groups:

Stachyospermae: Ovules are located on a stem or axis (where 'stachys' means spike/axis, and 'sperma' means seed). This group typically features simple, needle-like, or fan-shaped leaves.
Phyllospermae: Ovules are located on leaves or leaf-like structures (where 'phyllon' means leaf, and 'sperma' means seed). This group typically features large, frond-like leaves.
Step 2: Detailed Classification:
Let's classify the provided orders according to this system:

Cordaitales: An extinct gymnosperm order, considered ancestral to conifers. Their ovules were axis-borne, classifying them as Stachyospermae.
Ginkgoales: Includes the extant {Ginkgo biloba}. The ovules are borne on stalks (axes), thus classifying this order as Stachyospermae.
Coniferales: This includes conifers (pines, firs, etc.). Their ovules are borne on scales, considered modified shoots or axes, placing them in Stachyospermae.
Cycadales: This includes the cycads. Their ovules are borne on modified leaves called megasporophylls. This leaf-borne characteristic places them in Phyllospermae, not Stachyospermae. Pteridospermales (seed ferns) also belong to Phyllospermae.
Step 3: Conclusion:
Cycadales belongs to Phyllospermae, not Stachyospermae. Therefore, Cycadales is the correct answer.