aplanospores: They are non-flagellate (non-motile) spores and sometimes interpreted as abortive zoospores. They are found in many Chlorophyceae and usually develop in unfavourable conditions. v) Hypnospores: They are very thick-walled aplanospores. They are perennating bodies. They are found in many green algae, e.g., Pediastrum. Parthenogenesis: Sometimes the perfect spores are attained without fusion and are called azygospores or parthenospores. Here the female gamete may give rise to a new plant without fusing with male gamete. The process is called parthenogenesis. This process has been recorded from several Chlorophyceae. Sometimes one species of the genus reproduces parthenogenetically and the other species does not, e.g., Ulva lactuca is parthenogenetic species and U. lobata is not. 3. Sexual reproduction: This may be divided into four main sub-types, i.e., (i) isogamy, (ii) Anisogamy, (iii) aplanogamy and (iv) oogamy. (i) Isogamy: This is the simplest and primitive type of sexual reproduction. Two morphologically identical flagellated zoogametes take part in fusion. Usually such gametes come from two different individuals. The resultants are zygospores. Isogamy is found in many Chlorophyceae, e.g., species of Chlamydomonas, Ulothrix, etc. (ii) Anisogamy: Here the gametes taking part in fusion are not identical. The gametes are flagellate. One gamete is smaller and the other larger in size. The smaller one is supposed to be male and the larger female. The resultants are zygospores. The examples of Anisogamy are found in several Chlorophyceae, e.g., Chlamydomonas braunii. (iii) Oogamy: This is the highest evolved type. There is union of small flagellate antherozoid with a large non-motile egg. The resultants are called oospores, e.g., Volvox, Oedogonium, etc. and several other Chlorophyceae. The species may be homothallic (monoecious), i.e., both male and female sex organs are present on the same plant, or heterothallic (dioecious), i.e., male and female sex organs develop on two different thalli. (iv) Aplanogamy: This is an unusual type found in order Conjugales. Here the amoeboid gametes (aplanogametes) fuse to each other and zygospores are resulted, e.g., Zygnema, Spirogyra, etc.

aplanospores

Aplanospores

aplanosprs is the answer