Isoetes, Linnaeus (1753:, 1100

Singh, Sarvesh Kumar, Shukla, Santosh Kumar, Dubey, Nawal Kishore & Shukla, Pradeep Kumar, 2018, Isoetes × gopalkrishnae (Isoetaceae), a new interspecific sterile hybrid from central India, Phytotaxa 362 (1), pp. 68-76 : 74

Key to species of Isoetes with retate, reticulate, rugulate megaspore and species growing in general area of I. × gopalkrishna e:

1. Megaspore with tuberculate ornamentation; velum absent................................................................................................................2

–. Megaspores with reticulate ornamentation; velum covering 3/4 or more of the sporangium............................................................3

2. Tubercles pointed and tri-radiate ridge bifurcate ................................................................................................................... I. indica

–. Tubercles rounded and tri-radiate ridge simple....................................................................................................... I. coromandelina

3. Reticulations restricted to the central part of the distal surface of megaspores; girdle smooth .............................. I. panchganiensis

–. Reticulation present over the entire distal surface; girdle not developed...........................................................................................4

4. Megaspores dimorphic ...................................................................................................................................................... I. reticulata

–. Megaspores trimorphic.............................................................................................................................................. I. rajasthanensis

5. Velum absent to rudimentary..............................................................................................................................................................6

–. Velum covering 1/2 to 3/4 of sporangium..........................................................................................................................................7

6. Megaspores with retate ornamentation; microspores with echinate ornamentation; velum rudimentary.................. I. mahadevensis

–. Megaspores with rugulate ornamentation; microspores with echinate to shortly cristate ornamentation; velum absent to rudimentary........................................................................................................................................................................... I. × gopalkrishnae

7. Muri generally forming areoles .................................................................................................................................... I. panchananii

–. Muri forming short cristae, rarely areoles .......................................................................................................... I. sampathkumaranii