Key to all the Rhizomyces

It should be noted that R. cornutus Thaxt., R. cucullatus Thaxt. and R. gibbosus Thaxt. are very closely related and the distinguishing characters (in brackets) reported in the key are those given with the original descriptions (Thaxter 1901, 1918, 1931).

1. Thallus not ramified, usually bearing a single perithecium (very rarely 2) ...................................... 2

¯ Thallus ramified, bearing more than one perithecium ............ R. ramosus W.Rossi & Feijen sp. nov.

2. Perithecium lacking any outgrowth or bulge near the apex ............................................................. 3

¯ Perithecium bearing an outgrowth or a bulge near the apex ............................................................ 9

3. Perithecial tip abruptly distinguished and blackened ....................................................................... 4

¯ Perithecial tip not abruptly distinguished and not blackened ........................................................... 5

4. Basal cell subsigmoid, bearing a depression ...................... R. forcipatus W.Rossi & Feijen sp. nov.

¯ Basal cell not as above .......................................................................................... R. crispatus Thaxt.

5. Thallus never reaching 1 mm in length, not bearing a rounded hausorium ..................................... 6

¯ Thallus very slender and elongate, exceeding 1 mm in length, bearing a rounded hausorium penetrating the exoskeleton of the host .......................................................... R. canzonerii W.Rossi

6. Thallus not bearing a haustorium penetrating the exoskeleton of the host ....................................... 7

¯ Thallus bearing a ramified haustorium penetrating the exoskeleton of the host .................................................................................................................. R. ctenophorus Thaxt.

7. Perithecium symmetrical or almost so .............................................................................................. 8

¯ Perithecium distinctly asymmetrical ..................................................................... R. confusus Thaxt.

8. Perithecial stalk-cell at least 3 times longer than the perithecium; appendage and perithecial apex reaching the same height, more or less ............................................................. ...... R. gracilis Thaxt.

¯ Perithecial stalk-cell about as long as the perithecium; appendage distinctly exceeding in length the perithecial apex ................................................................................................. R. kamerunus Thaxt.

9. Perithecium bearing a rounded bulge or a short outgrowth just below the apex ............................ 10

¯ Perithecium bearing a divergent, elongate, finger-like outgrowth just below the apex ................................................................................................................ ...... R. circinalis Thaxt.

10. Thallus bearing a ramified haustorium penetrating the exoskeleton of the host.............................11

¯ Thallus not bearing a haustorium penetrating the exoskeleton of the host ......................................... .............................................................................................. R.tschirnhausii W.Rossi&Feijensp. nov.

11a.Perithecial outgrowth “relatively narrow and tooth-like” .................................... R. cornutus Thaxt.

11b.Perithecial outgrowth “slightly curved outwards, resembling a peaked hood” ...................... ...................................................................................................... R. cucullatus Thaxt.

11c.Perithecial outgrowth “broadly rounded and divergent” ..................................... R. gibbosus Thaxt.