The St Albans opener hit up 82 in 110 balls at Hagley 3 on Saturday in a commanding innings, which included 12 fours and two sixes.
He looked to be heading for a big hundred before being stumped in an unusual manner, going down the wicket to spinner Steve McCloy and getting an inside edge along the ground to the keeper.
Cumming was third out at 147 in the 31st over, but his team-mates carried on the momentum for the side to reach 268 for nine. Steven Knox scored 46 from 65 balls and No. 7 batsman Gareth Brooks 34 not out from just 27, with five boundaries.
Marist's opening bowler, Simon Grainger, took three wickets, but conceded 55 from his 10 overs.
That total always looked too much for Marist, which was dismissed for 144 in the 43rd over. Seven batsman reached double figures with only Grainger and Chris O'Connell getting into the 20s.
Most of the damage was done by St Albans left-arm spinner James Ward with four for 36.
St Albans still shares the lead with High School Old Boys and Riccarton, but the first two teams have yet to have their byes,
Riccarton win close contest
At Garrick Park, Riccarton and Lancaster Park-Woolston had the closest contest of the round, the home side falling only 33 runs short of the big Riccarton total of 262 for nine.
At 228 for eight after 45 overs, Lancaster Park-Woolston was ahead of Riccarton's score at the same stage, but was dismissed in the 47th over. No. 3 batsman Steve Gibson was the main contributor, his 58 coming off 80 balls.
Glenn Foulkes, the sixth bowler used by Riccarton, took the last three wickets in seven balls with his in-duckers, markedly improving his figures from none for 25 from three overs to three for 26 off 4.1 overs.
More than half Riccarton's runs came in a mighty third-wicket stand of 140 in 152min between Robbie Frew (59 from 91 balls) and Aftab Habib (67 from 69 balls, including five fours and a six).
For Lancaster Park-Woolston, Wade Cornelius and John Quinn took six of the nine wickets.
Sydenham collapses
Old Boys would not have been entirely happy with their total of 196 for seven at Hagley 1, with middle-order batsman Robert Miller (41 not out from 48 balls) the only one to score more than the 34 extras.
James Barrett and Sam Foley put on 56 for the third wicket in the best stand.
Those runs were more than enough for Sydenham, which collapsed after Andrew Thin and Kieran White had put on 30 for the first wicket. The next seven wickets fell for just 12 runs before No. 8 batsman Todd Harris led some resistance with his 23 not out, including three fours.
Old Boys opening bowler Sam Davis made the early inroads with three for 20 from six overs and Miller had a nice double, taking two for none from eight balls of left-arm spin.
Hastings hits 51
In the only match not to have a rain-delayed start, Burnside-West University had nearly 20 overs to spare when it reached the required 152 against Old Collegians at Burnside Park.
It was all smooth sailing for Burnside-West after a first-wicket partnership of 80 between Mark Hastings and Sean Craig. Hastings had nine fours and a six in his 51.
An unbeaten 35 from Matt Everest, with five fours and one six, guided Burnside-West to the win with six wickets in hand. John Hampton was the best of the Collegians bowlers with two for 28 off six overs.
Old Collegians had done extremely well to set a semi-respectable target after crashing to 84 for eight before the last two partnerships nearly doubled the score. David Cartwright and Simon Harding (17no) put on 23 and then Harding combined with No. 11 Hampton for an unbroken stand of 44.
Cartwight's 28 included three sixes, two hoisted from the bowling of medium-pacer Hastings, who still managed one for 25 off his 10 overs. Hamish Kember had the remarkable figures of 10-6-7-1 with his left-arm spinners.
Short scoreboards
Riccarton 262-9 (R Frew 59, A Habib 67, W Stead 32; W Cornelius 3-33, J Quinn 3-45) beat Lancaster Park-Woolston 229 in 46.1 overs (S Gibson 58, R Tibbotts 39, C McGillivray 29, J Hindson 28; W Stead 2-37, H Shaw 2-36, P Monk 2-51, G Foulkes 3-26) by 33 runs.
Old Collegians 151-9 (M Rountree 22, D Cartwright 28, J Hampton 26no; C Ogilvie 3-38, D Maxwell 3-18) lost to Burnside-West University 152-4 in 30.1 overs (M Hastings 51, S Craig 27, M Everest 35no; Hampton 2-28) by six wickets.
St Albans 268-9 (C Cumming 82, S Knox 46, G Lucas 22, G Brooks 34no; S Grainger 3-55, C Bird 2-44) beat Marist 144 (Grainger 23, C O'Connell 21; J Ward 4-36, M Griffin 2-22) by 124 runs.
High School Old Boys 196-7 (B Yock 21, J Barrett 32, S Foley 21, R Miller 41no; K White 2-45, G O'Reilly 2-30) beat Sydenham 84 in 35.2 overs (A Thin 23, T Harris 23; S Davis 3-20, Miller 2-0) by 112 runs.
East-Christchurch Shirley bye.
Points after seven rounds (*denotes team has had bye):
Riccarton 10*, HSOB 10, St Albans 10, Lancaster-Park Woolston 6*, Burnside-West University 6*, East-Shirley 4*, Old Collegians 4*, Marist 4*, Sydenham 2*.